Prompted by recognition of the potential of chemotherapy to increase the success of testis conserving surgery in patients with germ cell cancer, background and outcome data are reviewed and their contribution to the ongoing debate about how germ cell cancer develops discussed. The review is based on three previous studies of: a) time trends in tumour size in 578 personal series of all stages of testis cancer treated since 1978; b) impact of chemotherapy on actuarial risk of tumours in contralateral testis examined on 1221 patients treated in trials through the Anglian Germ Cell Cancer Consortium; and c) testes conservation attempted using chemotherapy in 78 patients. Since 1978 tumour size has decreased from 4.8 to 3.0 cms while cure has gone from 77 to 97%. There was no overall long term reduction in second cancers beyond 10 years in stage 1 patients after orchidectomy alone compared to stage 1 or metastatic disease patients receiving chemotherapy though the incidence was non significantly lower up to 10 years particularly in those patients receiving etoposide based combination. Testis conservation was initially successful in 28 of 78 (36%). An additional 25 (32%) had no viable cancer in orchidectomy specimen. In the 28 primary tumours cured by chemotherapy there was a 26% late relapse rate between 5 and 10 years (all cured by orchidectomy) compared to less than 5% in those cured with established metastases. In conclusion, testis conservation with chemotherapy is safe and feasible, though relapse is too frequent for routine service use. Confirmation of the high frequency of late relapse by others has raised the question whether these recurrences are due to post pubertal events reinducing CIS in intrauterine oestrogen primed germ cells and highlights the potential of testes conservation studies to better understand germ cell cancer development.