Background: Bardet-Biedl syndrome (BBS) is a heterogeneous genetic disorder that comprises numerous features, including renal cystic disease. Twelve BBS genes have been identified (BBS1–12). Although the exact functions of the BBS proteins are unknown, evidence suggests that they are involved in cilia assembly, maintenance and/or function. Renal primary cilia dysfunction can lead to cystic kidney disease. To test whether lacking Bbs4 affects cilia assembly and structure, we analyzed primary cilia in Bbs4-null (Bbs4<sup>–/–</sup> ) mice. Methods: Renal tubule cultures from wild-type (Bbs4<sup>+/+</sup> ) and Bbs4<sup>–/–</sup> mice were examined by immunocytochemistry and scanning and transmission electron microscopy. Results: Our culture conditions generated ciliated epithelial cells that were mostly of collecting duct origin. The microtubule ultrastructure of cilia and basal bodies did not appear disrupted in Bbs4<sup>–/–</sup> cells. In control cells, cilia length was maximal at 7 days in culture. In cells cultured from Bbs4<sup>–/–</sup> mice, cilia were shorter initially, but surpassed the length of control cilia by 10 days. Renal primary cilia were also longer in Bbs4<sup>–/–</sup> kidneys. Conclusions: Lacking Bbs4 does not lead to aberrant cilia or basal body structure. However, the dynamics of cilia assembly is altered in Bbs4<sup>–/–</sup> cells, suggesting a role for Bbs4 in the regulation of ciliary assembly.