This volume collects the invited lectures and some selected contributions presented at the 5th International Meeting on Clinical Pharmacology in Psychiatry, which was held 26-30 June 1988 at the University of Troms0, Norway. The 24 h of daylight at the northernmost university in the world al- lowed for long, pleasant and productive sessions. The title of the conference as well as a number of the topics covered represent a continuation of four previous conferences, the first held in Chicago in 1979 and organized by the late Earl U sdin and colleagues. The earlier conferences have been documented in Clinical Pharmacology in Psychiatry, edited by E. Usdin (Elsevier, New York, 1981), Clinical Pharmacology in Psychiatry. Neuroleptic and Antidepressant Research, edited by E. Usdin, S. G. Dahl, L. F. Gram and o. Lingjrerde (Macmillan Publishers Ltd., London, 1981), Clinical Pharmacology in Psychiatry. Bridging the Experimental-Therapeutic Gap, edited by LF. Gram, E. Usdin, S.G. Dahl, P. Kragh-Sorensen, P. L. Morselli and F. Sjoqvist (Macmillan Publishers Ltd., London, 1983), and Clinical Pharmacology in Psychiatry. Selectivity in Psychotropic Drug Action - Promises or Problems? edited by S. G. Dahl, L.F. Gram, S.M. Paul and W.Z. Potter (Psychopharmacology Series 3, Springer, Heidelberg, 1987).