In the summer of 1995, the First International Behavioral Development Sym-
posium: Biological Basis of Sexual Orientation and Sex-Typical Behavior
was held in Minot, North Dakota. The symposium was made possible by a
grant from the Eugene Garfield Foundation of Philadelphia in cooperation
with Minot State University. The purpose of the conference was to provide a
forum for researchers who are at the forefront of research on biological con-
tributions to variations in sexual orientation and other sex-typical behavior,
to exchange their latest scientific findings and interpretations.

A fundamental premise upon which the conference was organized is that
sexual orientation and sex-typical behavior patterns can be fully understood
only within a biological context. This premise is in accordance with growing
evidence that all sorts of genetic, hormonal, and neurological factors impinge
on sexual orientation (see Ellis, 1996a; Ellis & Ames, 1987; LeVay, 1993)
and sex-typical behavior patterns ( Ellis, 1986; Halpern, 1995).

The present book offers a collection of chapters based on papers presented
at the symposium primarily that pertain to sexual orientation. A second book
based on this conference that focuses on sex-typical behavior entitled Males,
Females, and Behavior will be published in 1998 (also by Praeger). Addi-
tional papers from the symposium will appear as a special issue of the Jour-
nal of Sex Research in 1997 (volume 34, number 2).

Our goal in editing this book is to provide readers with research findings
and theoretical interpretations that are on the leading edge of the scientific

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