Human nasal epithelial cells, which lost their cilia in monolayer cultures, redeveloped cilia after 1 week in a suspension culture system. Before ciliogenesis started, the number of microvilli increased. Primary cilia were absent. The different cytoplasmic stages of this in vitro ciliogenesis could be reconstructed here into a sequence of events comparable to that described in the embryogenesis of the mammalian respiratory tract. In addition to the fibrogranular aggregates, deuterosomes with procentrioles and kinetosomes, small tubular structures in the fibrogranular aggregates could be visualized. The formation of the ciliary shaft above an aligned basal body started as an elevation of the apical membrane without any recognizable axonemal ultrastructure. This study provides the first full description of in vitro ciliogenesis on a human tissue.