Physical trace reports were labeled Close Encounters of the Second Kind (CE-II) by J.Allen Hynek and involve instances where there was a physical interaction between the UFO and its environment. Usually these involve a landing trace, such as depressed grass or soil, but also burned or broken vegetation, residues, and more exotic traces. There are at least somewhere between 3,500 and 5,000 UFO physical trace cases.

Ted Phillips' Physical Trace Catalogue
by Paul Fuller
These selections from the Ted Phillips Trace Catalogue originally appeared in several editions of the Crop Watcher magazine. and were compiled by British researcher, Paul Fuller. (Contains a selection of cases from Ted Phillips' Physical Trace Catalogue). The catalogue was published in 1975 by CUFOS and its proper title is Physical Traces Associated with UFO Sightings, A Preliminary Catalogue.

A Catalogue of Australian Physical Trace Cases
Compiled by Keith Basterfield
This catalogue brings together many of the (Australian) cases where traces have been placed in a UFO context-even if a UFO was not reported in association with the event.

A Catalogue of Australian Physical Trace Cases (selected cases with further details)
Bill Chalker
The catalogue of Australian physical trace cases compiled by Keith Basterfield and Bill Chalker lists 147 cases covering the period from 1927 to 1997. Physical trace events with probative UFO correlation, i.e. 38 possible type 1 physical traces cases (Chalker, 1979 & 1987), are listed here to draw attention to cases of potential significance.

A Report on the Investigation of Magnesium Samples From a UFO Explosion Over the Sea in the Ubatuba Region of Brazil
Olavo T. Fontes M.D (published in Coral Lorenzen's "Flying Saucers: The Startling Evidence Of The Invasion From Outer Space), reprinted on Temporal Doorway website
Near the Brazilian coast, it was said a disc shaped object had exploded over the seashore. It was said a disc shaped object had exploded over the seashore. Fragments recovered from the explosion were supposed to have fallen, while burning, into shallow waters, which, according to the witnesses, quenched the fire and allowed recovery.

Australian UFO Physical Trace Cases - A Review
Bill Chalker
The physical trace phenomenon is an enduring aspect of the UFO mystery, having manifested for the entire duration of the modern era of the UFO controversy. And like the UFO phenomenon itself, it is global in its extent. This range of events appears to substantiate the contention that UFOs possess a physical dimension.

Biochemical traumatology as a potent tool for identifying actual stresses elicited by unidentified sources: Evidence for plant metabolic disorders in correlation with a UFO landing
by Bounias, Michel C. L. (1990), J. Scientific Exploration, Vol. 4, No. 1, p. 1.
Following an accurate testimony of a "UFO" landing, samples of a wild strain of Alfalfa were collected at the epicentre and at various increasing distances of the trace left on the ground 4 and 40 days after the observation. A

Physical Evidence Related to UFO Reports (Sturrock Panel): Ground Traces
Peter Sturrock / Sturrock Panel Report / Physical Evidence Related to UFO Reports
A few of the reports that have been investigated by GEPAN/SEPRA show ground traces that may be associated with the events reported by witnesses. Similar cases have been documented by other investigators. Phillips (1975) prepared a catalog of 561 such cases as a CUFOS report. R

Physical Traces Associated with Unidentified Flying Objects: An Interim Report - Results of Processing Data - 1490 - 2004
Ted R. Phillips, Center for Physical Trace Research
This report presents a statistical analysis of data given in 3,059 reports involving observations of anomalous phenomena or objects on or near the ground resulting in physical residues generated by the observed phenomena or objects. These observations took place in 91 countries between 1490 and 2004. R

Top Physical Trace Cases - Cases of High Strangeness - A Preliminary List
Ted Phillips, Center for Physical TraceResearch
The following is a preliminary list of High Strangeness cases involving physical traces associated with UFO sightings. It is not complete and will be added to as additional reports are received. These cases represent some of the high strangeness trace/landing events from a database of over 4,000 such events. R

Center for Physical Trace Research, Ted Phillips Website
The Center for Physical Trace Research was established June 1, 1998 by Ted Phillips to provide a central repository for the receipt, study, and distribution of UFO landing events involving physical residue. Phillips has worked on hundreds of such cases since 1969 with the late Dr. J. Allen Hynek and the Center for UFO Studies, as well as with Mutual Unidentified Flying Object Network, Incorporated, MUFON.

Map: UFO Landings & Traces: Europe .. all dates.
Larry Hatch, U UFO Database
UFO sightings on this map are restricted to Landings and Trace Cases in Europe for all dates. For once, France does not dominate the map entirely. Italy and England register about an equal density of landings and traces; Spain and Portugal nearly so.

Map: UFO Landings & Traces: North America
Larry Hatch, U UFO Database
UFO sightings on this map are restricted to Landings and Trace Cases in North America for all dates. "Landings" are defined as actual touchdowns, or cases where the UFO came within a few feet of the ground or water. Physical Traces are just that, marks, burns and other notable effects on soil, plants, animals, structures ..

NICAP Landing/Trace Cases
NICAP (National Investigative Committee on Aerial Phenomena)
A listing of several physical trace cases as well as other physical trace case catalogs, articles and documents.

Physical Trace Case: Manitoulin Island, Ontario (Canada)
Strange Days Indeed
A physical trace case near Spring Bay, Manitoulin Island which was discovered in mid-September 1990. This site has quality photographs from the case.