Gametogenesis involves mitotic expansion of stem cells, followed by meiotic recombination of genetic information. Specific gene expression subsequently results in construction of highly specialized gametes, containing a haploid genome. Gametogenesis requires hormonal control (gonadotropins, steroid hormones) through hormone action on supporting somatic cell types. Human infertility is observed in 10-15% of all couples, with about equal contribution of male and female factors. The emphasis of our current research is on the male (mouse and human), but the animal studies also involve oogenesis and oocyte quality. Much attention is given to gametogenic gene expression and chromatin rearrangement. A major aim of the program is to improve diagnosis of (molecular/genetic) causes of human infertility. This is highly relevant, also in the context of application of assisted reproduction, and molecular/genetic evaluation of possible risk factors associated with this technology. The program incorporates research on medical/physical aspects of male sexual dysfunction. New initiatives include studies on germ cell transplantation and gametogenic genome instability. Recent collaboration with chemical and pharmaceutical companies addresses effects of exogenous compounds on male fertility, and development of a non-hormonal method for male contraception. The program is characterized by close collaboration between Urology / Sexology / Andrology / Gynaecology / (Clinical) Genetics.