The 6th triennial meeting of the International Study Group for Tryp- tophan Research (ISTRY) was held May 9-12, 1989 in Baltimore, Maryland (USA). From the wide variety of topics and disciplines represented, as documented in this volume, it is clear that tryptophan research and ISTRY are alive and well. ISTRY traces its or1g1ns to at a tryptophan symposium organized in 1971 by H. Schievelbein at Hohenried near Munich (Germany). Up to that time there had been occasional international tryptophan conferences at irregular inter- vals. A number of participants at the Hohenried meeting felt that an inter- national tryptophan organization should be formed to organize regular meet- ings and to foster collaboration and information exchange on tryptophan-re- lated topics. Thanks mainly to the founding work of H. Schievelbein and W. Kochen, an executive committee was elected and ISTRY was born. The inaugural meeting in 1974 was held in Padova (Italy) to honor L. Musajo, one of the foremost pioneers in tryptophan studies. This first ISTRY meeting was suc- cessfully organized by L. Musajo, G. Allegri, A. De Antoni, and C. Costa, and was critical in assuring the viability of the new organization. Subsequent meetings were held in 1977 in Madison, Wisconsin (USA), organized by R.R. Brown, D.P. Rose, and W.E. Knox, honoring C.P. Berg; 1980 in Kyoto (Japan), organized by O. Hayaishi, R. Kido, Y. Ishimura, T. Deguchi, T. Hino, T.