Studies were conducted into behaviours of total and extracellular hyaluronidase activities of bull semen under selected incubation phenomena. Particular attention was given to effects generated by media of high and physiological ion strengths (385 mosm and 305 mosm), in vitro capacitation treatment, and effects of various washing techniques as well as incubation temperatures. Total hyaluronidase activity was clearly lowered in washed ejaculate sperms, as compared to original sperm, with extracellular enzyme activity, however, being unchanged. Hyaluronidase activity was also lower in deep-frozen sperm. Increase in extracellular and total hyaluronidase activity was at its highest under the impact of cattle serum albumin and with a defined temperature-time regime (four hours of comparative incubation in a medium of physiological ion strength at 35 degrees C, 37 degrees C, 39 degrees C, 41 degrees C, and 45 degrees C). Release of hyaluronidase was most clearly inducible after pretreatment in medium of physiological ion strength and by four hours of incubation at 39 degrees C. The preliminary conclusion is that the values so far recorded appeared to reflect some superimposition of physiological and degenerative processes which could not be distinguished from each other under the experimental conditions chosen for the studies.