Early serum tumor marker decline (STMD) during chemotherapy was shown to predict survival in patients with poor prognosis non-seminomatous germ cell tumors (GCT) in the first line. The aim of the study was to assess the prognostic value of STMD in relapsed GCT;s patients. From January 1995 to December 2007, all patients treated for GCT s with salvage therapy at the National Cancer Institute of Slovakia were identified from the tumor registry database and screened retrospectively for serum AFP and betaHCG level at the time of relapse. STMD rate was calculated for each patient and each tumor marker with an abnormal marker value at baseline and each tumor marker M (HCG or AFP) using only two values: the baseline value (M0) and the value obtained after one cycle of chemotherapy (day 21 value; M1). The decline rate was calculated using a logarithmic transformation, and it was expressed as a theoretical number of weeks necessary to normalization that was called predicted time to normalization. Decline rates were classified into "favorable" or "unfavorable". Totally, 75 patients were identified, 39 had favourable (group A) and 36 unfavorable (group B) STMD. The 2-year and 5-year PFS rates were 61% and 58% for group A and 17% and 7% group B (p<0.00001). Of all the baseline characteristics that were included in the Cox model, STMD was the most important predictor of PFS and OS. We suggest that STMD is strong independent prognostic factor in GCT patients treated with salvage chemotherapy. Prospective studies of different approaches in this patient's population based on STMD are warranted.