The semaphorin/collapsin family of proteins comprises molecules thought to be important for the guidance of growing axons. All members of this family, which includes both secreted and cell-surface molecules, share a conserved domain of approximately 500 amino acids. Here, we report the cloning of a novel murine semaphorin, termed M-sema IV. It displays 96.3% identity to the human semaphorin H-sema IV and is therefore likely to be the respective murine homologue. In addition, an isoform was identified, which contains an additional 31 amino acids in the semaphorin domain. M-sema IV appears to be expressed ubiquitously in adulthood. During embryogenesis, in situ hybridization revealed M-sema IV expression in subregions of the central nervous system and various other tissues like skin, kidney, lung and intestine.