Using RNA in situ hybridization we compared the expression patterns of the cell adhesion molecule-like receptor-type protein tyrosine phosphatases LAR, RPTPδ and RPTPσ during mouse development. We found that LAR is expressed in basal lamina-associated epithelial tissues of (neuro)ectodermal, neural crest/ectomesenchyme and endodermal origin. RPTPσ is found in (neuro)ectodermal, neural crest-derived systems and in mesoderm-derived tissues. The expression pattern of RPTPσ largely parallels that of RPTPσ, in concordance with their proposed evolutionary history (Schaapveld et al., 1995).