Accumulation of transcripts from N-ras and unr genes was comparatively analyzed during the development of germline and somatic tissues. Northern blots on fetal and postnatal samples from somatic tissues, including brain, skeletal muscle, liver, kidney, small intestine and heart were studied together with ovaries and testis. While the expression of N-ras was rather stable all along the development of the different tissues analyzed, the expression of unr exhibited a specific pattern in some tissues. Specifically, in testis, there is a developmental regulation of the relative accumulation of the three alternative transcripts. Unr has a relative high expression in testes and heart but the accumulation seems to be different for the different size transcripts in each case. However, the expression in small intestine is practically absent in adults. From the comparative analysis of the expression of both genes, N-ras and unr, we propose that the regulation of N-ras is not directly coordinated with unr expression during the development. However, the expression of unr and its alternative transcripts is developmentally and differentially regulated in small intestine, heart and testis. The change in the pattern of accumulation during testis development from long to small alternative transcripts, could be interpreted in terms of possible alleviation of transcription interference of N-ras.