It has been recognized that the tumour markers alpha-fetoprotein (AFP) and human chorionic gonadotrophin (HCG) may show a transient elevation after the initiation of chemotherapy in non-seminomatous testicular cancer. We investigated the prognostic importance of these so-called marker surges in a cohort of patients treated with cisplatin combination chemotherapy between 1983 and 1991. A total of 669 patients were studied. Of 352 patients who had an elevated AFP at the start of treatment and for whom we had data at both day 1 and day 8, 101 (29%) had a surge. Of 317 patients for whom we had data for HCG, 80 patients (25%) had a surge. It was found that an AFP surge was a strong adverse prognostic factor for progression [hazard ratio (HR) 2.28, P=0.005]. There was no statistically significant difference in survival (HR 1.65, P=0.13). There was no prognostic significance of a HCG surge, either for progression or for survival. To investigate whether a surge was an independent prognostic factor for progression and survival, multivariate Cox regression models were fitted using the independent prognostic factors for progression and survival and the surge/decline variable. An AFP surge was retained in the final model for progression. A HCG surge was of no prognostic importance for progression or survival. We conclude that an AFP surge has an adverse prognostic significance, independent of pretreatment characteristics.