The in vitro hemolytic activity of 4 isolates of Trichomonas vaginal& was investigated. Repetitive hemolysis assays of any one isolate showed cyclical fluctuations in hemolytic activity, varying over 24 hr of continuous culture. Maximal hemolytic activity was detected using trichomonads in the lag phase of the growth cycle. Investigations showed that hemolysis was a contact-dependent phenomenon and microscopic investigation of samples showed a significant correlation between hemolysis and

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... ment of erythrocytes to the trichomonad surface. Quantitative data from cytoadherence assays using [5~Cr]-labeled erythrocytes were consistent with these observations. It is suggested that hemolytic activity is dependent upon adherence of red blood cells to the surface of T. vaginalis.