P53 tumour suppressor gene mutations occur in approximately 50% of common solid tumours such as breast, colon and lung. In contrast, p53 gene mutations occur infrequently (< 3%) in germ cell tumours, even though p53 protein is expressed at high levels in the vast majority of tumour samples. P53-regulated genes are not correspondingly over-expressed in germ cell tumour samples and cell lines, indicating that p53 functions poorly as a transcription factor in this tumour type. High levels of wild-type p53 may contribute, in part, to the chemosensitivity of germ cell tumours.