The majority of ovarian cancer patients with advanced disease at diagnosis will relapse following primary treatment, with a dismal prognosis. Monitoring the levels of serum markers in patients under follow-up may be essential for the early detection of relapse, and for distinguishing high-risk patients from those with less aggressive disease. The aim of the present study was to investigate the possible predictive value of human epididymis protein 4 (HE4) and carbohydrate antigen 125 (CA125) in relation to recurrence of epithelial ovarian cancer by measuring the two markers during follow-up subsequent to surgery and adjuvant first-line carboplatin/paclitaxel chemotherapy. Serum HE4 and CA125 were analyzed in 88 epithelial ovarian cancer patients at the end of treatment and consecutively during follow-up. The patients were divided into a high-risk and a low-risk group based on having an increase in HE4 and CA125 levels above or below 50% during follow-up, relative to the baseline (end-of-treatment) level. Disease recurrence was detected in 55 patients during follow-up. Patients with an increase in HE4 of >50% at 3- and 6-month follow-up compared to the end-of-treatment sample had significantly poorer progression-free survival (PFS) [hazard ratio (HR), 2.82 (95% CI, 0.91-8.79; P=0.0052) and HR, 7.71 (95% CI, 3.03-19.58; P<0.0001), respectively]. The corresponding 3- and 6-month biomarker assessments for increased CA125 levels (>50%) showed HRs of 1.86 (95% CI, 0.90-3.80; P=0.0512) and 2.55 (95% CI, 1.39-4.68; P=0.0011), respectively. Multivariate analysis confirmed HE4 as a predictor of short PFS, with an HR of 8.23 (95% CI, 3.28-20.9; P<0.0001) at 6-month follow-up. The increase of CA125 was not a significant prognostic factor in multivariate analysis for PFS. In conclusion, HE4 appears to be a sensitive marker of recurrence and instrumental in risk assessment during the first 6 months of follow-up.