We explored the possibility that defects in the rhodopsin kinase gene might cause retinitis pigmentosa (RP) by evaluating 160 unrelated cases with dominant RP and 151 unrelated cases with recessive RP. One of five missense changes was discovered in each of six cases of dominant RP, but none of the missense changes cosegregated with disease among relatives. Heterozygous missense changes were found in two cases of recessive RP, and a heterozygous frameshift mutation was found in one additional case of recessive RP. Although the same DNA sequence alterations could be found heterozygously in the only affected sibling of each index case of recessive RP, no defect could be found in the other allele. Hence, none of the changes found in the cases of dominant or recessive RP was proven to be a cause of RP. The data indicate that defects in the rhodopsin kinase gene causing RP are either rare or nonexistent.