panied by material residues shows a broad distribution of natural elements, many of which are metallic in nature. They can be roughly described as be- longing in two categories: ªlight materialsº of high conductivity such as alu- minum, and ªslag-like materialsº reminiscent of industrial byproducts. Most of the cases under consideration strive to meet four criteria: 1) the literature gives sufficient ground to support the fact that an unusual aerial phenomenon occurred, 2) the circumstances of the actual recovery of the specimen are re- ported, 3) there is data to suggest that the specimen is in fact linked to the ob- served aerial object, and 4) physical analysis has been performed by a compe- tent laboratory of known reliability. In several instances the sample is available for continuing study by independent scientists. In the absence of a firm chain of evidence and of professional field investigation, most cases cannot lead to a definite conclusion about the nature of the phenomena that gave rise to each specimen, but much can be learned from the methodology involved in such analysis. Furthermore, compilation of similar cases on an expanded basis may eventually lead to the discovery of underlying patterns.

The combination of a reliable sighting of an unexplained aerial object with the recovery of a durable physical specimen is rare. While the media often allude to sensational finds and at least one former military intelligence officer has stated that he once had custody of advanced technology coming from a ªcrash,º (Corso, 1997) the material is not available for independent study and the details of its composition are scanty and contradictory.

At a more modest level, in the course of their investigations of the phenom- enon around the world, civilian researchers acting privately have patiently as- sembled the embryo of a sample collection, starting from physical specimens reportedly gathered at the site of a close encounter or ªmaneuverº type sight- ing.2

The present paper summarizes the data, stressing methodology while re- fraining from proposing premature explanations for the origin of the samples. We strived to find those cases where 1) the literature gives sufficient ground to

support the fact that an unusual aerial phenomenon occurred, 2) the circum- stances of the actual recovery of the specimen are reported, 3) there is data to suggest that the specimen is in fact linked to the observed aerial object, and 4) physical analysis has been performed by a competent laboratory of known reli- ability. In several cases the sample is available for continuing study by inde- pendent scientists. In the present paper we will try to establish the frequency of such cases and the type of analysis they suggest. In conclusion we will exam- ine hypotheses that may deserve further testing.

In an excellent catalogue compiled by Mr. Larry Hatch3 and made available to researchers and to the general public one finds 15,181 unexplained aerial phenomena reports that have been tabulated in computer-readable form. We have broken down these cases according to the classification system used by this author (Vallee, 1990) in order to bring out the distribution of incidents across various situations. Under this classification, inspired from Hynek’s def- inition of close encounters (Hynek, 1972), each case is given a type and a cate- gory. Hynek used a single digit representing the ªkindº or type of incident, ranging from ª1º for a simple sighting and ª2º for physical effects to ª3º for re- port of a lifeform or living entity. We have extended this typology using ª4º in cases when witnesses experienced a transformation of their sense of reality (often corresponding to the popular characterization of the incident as an ªab- ductionº) and ª5º in cases of lasting physiological impact, such as serious in- jury or death.

The categories to which the typology is applied range from ªCEº for close encounters and ªMAº for maneuvers (trajectory discontinuity) to ªFBº for fly- by (no observed discontinuity in flight) and ªANº for simple anomalies in which no UFO was reported: unusual lights or unexplained entities fall into this last category.

Using this classi®cation we would speak of a particular case as a CE-3 inci- dent, or a MA-2 incident,etc., leading to the simple matrix of Table 1, which provides a convenient way for establishing a baseline in comparing reports from various countries or from various epochs.

lobrand von Ludwiger and Mr. John Schuessler for help in analyzing materials or in communicating de- tails of their own findings on various sam ples mentioned in this article. We owe recognition to pioneers of this research, such as Dr. Olavo Font†s in Brazil and Jim and Coral Lorenzen in the U.S. Assistance from Messrs. Robert Allen, Ricardo Vilchez, Richard Masilko and Mark Uriarte in securing access to various specimens is gratefully acknowledged. Several correspondents, notably Robert Kincheloe, Pierre Lagrange, James McCam pbell, and Joe Roser, have called the author’s attention to important doc- uments and research ideas.

of the catalogue, broken down as follows: 90 are associated with simple anom- alies, 19 with a fly-by, 1,782 with maneuvers and 1,284 with close encounters. It should be noted that we are using the January 1997 version of the Hatch cat- alogue, which is an evolving entity. Statistics performed on other versions may differ from those given here.