In the article by Hiramoto et al. (1997) (Stage-specific expression of a mouse homologue of the porcine 135 kDa alpha-D-mannosidase (MAN2B2) in type A spermatogonia, Biochem. Biophys. Res. Commun. 241, 439-445) a new homologue to the porcine epididymis-specific 135 kDa alpha-D-mannosidase (MAN2B2) was cloned from a mouse testis cDNA library. Northern blot analysis with RNA of different tissues showed a testis-specific expression by using a mouse MAN2B2 oligonucleotide. In situ hybridization revealed that the mouse MAN2B2 transcript is localized exclusively in spermatogonia. In consequence to this it was proposed by Hiramoto et al. that the mouse MAN2B2 homologue could serve as a marker for spermatogonia. By repeating the published experiments we observed a different expression pattern of the mouse MAN2B2 gene. Northern blot analysis with either testicular RNA from prepubertal males or with testicular RNA from the W/W-v-mutant mouse which lacks germ cells showed an expression of the MAN2B2 gene. Furthermore, Northern blot analysis with RNA from different somatic tissues revealed that; the gene is ubiquitously expressed. Therefore, our refinement clearly demonstrates that the MAN2B2 mouse homologue is not specifically expressed in spermatogonia.