The adherence activity of Streptococcus agalactiae (group B) strains is directly dependent on the biological state of cultures. The aim of the present paper was to consider the effect of repeated transfers of cultures alternately on solid and liquid media and the effect of the growth phase. The strains, adhering weakly, strongly and variably to epithelial cells were employed in studies on the effect of repeated transfer. The percentage of adherent epithelial cells differed significantly after the first or the second transfer. On storage of the strains after the 3rd transfer at 4 degrees C for 4 d, the adherence activity decreased to the level of non-transferred strains. Ultrastructural analysis revealed in all strains the presence of capsular material, its character being similar both in strongly and in weakly adhering cultures. In weakly adherent strains, the structure of the capsular layer has not changed during transfer whereas the adherence of the strain increased considerably. The effect of the growth phase was studied during 3-48 h of incubation. The growth phase did not influence the adherence activity in strains that had been allowed to multiply for 3-24 h. After a long-term multiplication beyond 24 h, the adherence activity gradually decreased.