A computerized pattern recognition system has been developed that is capable of identifying 40 separate spontaneously occurring behavioral acts of the primate Macaca fascicularis. The system, called PROBE (pattern recognition of behavioral events), is described in detail. In its present stage of development, PROBE classifies behavioral activity with a reliability comparable to trained human observers. The potential applications for and improvements to the PROBE system are discussed.Techniques used in computer graphics and pattern analysis have been applied to the tasks of observing, classifying, and recording spontaneous behavioral activities in the captive primate. The goal in designing this system was to provide a computer-based pattern recognition system capable of identifying normal activity patterns of the primate Macaca [ascicularis. If successful, this system can be used to detect alterations in these patterns under conditions of toxicologic and pharmacologic insult. In this article, the development of our system, which is called PROBE (pattern recognition of behavioral events), is discussed.Throughout this project, the purpose was to solve a unique application problem. Existing pattern recognition methods (Fu, 1968;Fukunaga, 1972;Pavlidis, 1977), consistent with the adequate solution of our problem, were applied. HARDWAREThe computer system consists of a Digital Equipment Corporation PDP-11/34 computer with a floatingpoint processor and 32K of core memory, a nine-track magnetic tape drive, card reader, line printer, console typewriter, Tektronics Model 4012 display scope, and a 44·million-word disk drive. A schematic view of the