The attachment of E. histolytica trophozoites from monoxenic TPS-medium to galss surfaces was studied at different temperatures and pH values and in the presence of cytochalasin B, colchicine, and vinblastine. At pH 7.0 and at 36°C optimal adhesion rates of the amebae were observed in the range from 80% to 95%. Marked inhibition of adhesion was noted at higher concentrations of cytochalasin B. The adhesion rate was reduced to 50% by 50 μg/ml CB. Higher dosages successively prevented nearly all adhesion. Colchicine was without any effect. Vinblastine had a certain low effect but only at very high dosage. The observations are consistent with the assumption that the adhesion process is at least partially mediated by cytochalasin-sensitive contractile microfilaments, whereas microtubuli are obviously not involved in the cellsubstrate adhesion. © 1979 Springer-Verlag.