The occurrence of testicular tumours was not statistically significant different between the two strains (Table 1), but they were detected earlier in male 129S6/SvEv Men1+/- mice than C57BL/6 Men1+/- mice (12 vs 18 months of age (P < 0.005, Fig. 1). The gene discussed is MEN1; the disease is neoplasm of testis.