The effects of taurine chloramine derivatives on initial aggregation of isolated platelets suspended in buffered saline were studied. Inhibition of ADP-induced aggregation in pure cell suspension depended on the structure of chloramine antiaggregants. The most effective of them was N,N-dichlorotaurine; its concentration needed for 50% inhibition of aggregation was about 0.1 mM. Weaker antiaggregants N-chloro-N-methyltaurine and N-chlorotaurine in a final concentration of 0.5 mM reduced platelet aggregation by only 10%. The studied chloramines considerably differed by their characteristics (velocity of the reaction with sulfur-containing groups of atoms). N,N-dichlorotaurine exhibited the weakest reactivity with methionine thioester group. In turn, the velocity constant with reduced glutathione was by 2-3 orders of magnitude higher than that of other chloramines. Antiaggregant effect of taurine chloramine derivatives was 2-fold higher in the presence of serum albumin, presumably due to special interactions of taurine chloramines in complex with albumin with platelets.