New neurons are continuously born in the dentate gyrus of the adult mouse hippocampus, and regulation of adult neurogenesis is influenced by both genetic and environmental determinants. Mice of the 129/SvJ strain have significantly less hippocampal neurogenesis than other inbred mouse strains [1] and do not perform well in learning tasks. Here, the impact of environmental stimuli on brain plasticity during adulthood of 129/SvJ mice was studied using 'enriched environments' where mice receive complex inanimate and social stimulation [2,3]. In contrast to our earlier reports on mice of the C57BL/6 strain - which are competent in learning tasks and in which environmental stimulation did not influence cell proliferation [4,5] - environmentally stimulated 129/SvJ mice were found to have twice as many proliferating cells in the dentate gyrus compared with mice in standard housing. Environmental stimulation fostered the survival of newborn cells in 129/SvJ mice; this effect had also been seen in C57BL/6 mice. Phenotypic analysis of the surviving cells revealed that environmental stimulation resulted in 67% more new neurons. In combination with our earlier results, these data indicate a differential impact of inheritable traits on the environmental regulation of adult hippocampal neurogenesis. In addition, we observed behavioral changes in environmentally stimulated 129/SvJ mice.