In quail oviduct, a 175K (K = 10(3) Mr) protein associated with striated rootlets was previously identified by Klotz and co-workers using monoclonal antibody CC310. As this monoclonal antibody recognizes several proteins on immunoblots of ciliated cells, we prepared a polyclonal antibody monospecific to the 175K protein by intrasplenic immunization of mice. Immunofluorescence study confirmed the distribution of the 175K protein at the apical part of the ciliated cell and its absence in other epithelial cells. Immunogold staining showed that this protein was strongly associated with the fibrillar axis of striated rootlets. The absence of labeling on striation suggested that rootlets were composed of several proteins, with one group forming the fibrillar axis and the second forming the striation. The formation of striated rootlets during ciliogenesis was studied using this polyclonal antibody. The 175K protein appeared at the beginning of centriologenesis in fibrillar material located around dense granules, and then around the generative complex. The formation of rootlets began at the basal pole of migrating basal bodies. The elongation of the rootlet axes took place when basal bodies were anchored to the plasma membrane.