When induced by in vivo oestrogen stimulation, ciliogenesis continues in culture in vitro of quail oviduct implants. Ultrastructure of ciliogenic cells was compared after culture for 24 or 48 h in the presence or absence of 10(-5) M-taxol. Taxol, which promotes polymerization and stabilization of microtubules, disturbed ciliogenesis, but formation of basal bodies was unaffected by the drug. Conversely, their migration towards the apical surface seemed to be slowed down or blocked and axonemal doublets polymerized onto the distal end of cytoplasmic basal bodies. They elongated and often constituted a more or less complete axoneme, extending between organelles in various orientations. These axonemes, often abnormal, were not surrounded by a membrane, with the exception of the transitional or neck region between the basal body and axoneme. The formation of membrane in this area resulted from the binding of some vesicles to the anchoring fibres of the basal body. They fused in various numbers, occasionally forming a ring, at the site of the transitional region, and exhibited the characteristics of the ciliary necklace. The association of basal bodies with vesicles or with the plasma membrane appeared to be a necessary signal for in situ polymerization of axonemal doublets. In addition, taxol induced polymerization of numerous microtubules in the cytoplasm, especially in the apical part of the cell and in the Golgi area. This network of microtubules may prevent basal body migration.