The present invention relates to the identification of a gene, now designated BBS4, that is involved in the genetic disease Bardet Biedl Syndrome (BBS), which is characterized by such diverse symptoms as obesity, diabetes, hypertension, mental retardation, renal cancer and other abnormalities, retinopathy and hypogonadism. The human BBS4 protein disclosed herein is 519 amino acids in length and is coded for by a gene spanning 16 exons. Homologs have been identified in mouse, rat, zebrafish. Methods of use for the gene, for example in diagnosis and therapy of BBS and in drug screening, also are described.