Cyclic nucleotide-gated cation channels are essential in visual and olfactory signal transduction. An additional member of the cGMP-gated channel family, termed CNG-3, has been cloned from bovine kidney. Its deduced amino acid sequence is 60% and 62% identical with the CNG-channel proteins from bovine rod outer segment and bovine olfactory epithelium, respectively. Northern analysis and sequences amplified by the PCR showed that the CNG-3 mRNA is present in testis, kidney, and heart. Calcium permeated the expressed channel in the presence of extracellular Mg2+ and Na+ at membrane potentials from -100 to +45 mV. It is likely that CNG-3 protein is responsible for cGMP-induced Ca2+ entry in cells other than sensory cells.