The Scandinavian countries exhibit some of the highest incidence rates of ovarian cancer in the world. Prognosis is poor, and the crude 5-year relative survival was 36% in the Nordic countries in the 1980s. Histology-specific prognostic trends in 5-year relative survival of patients with ovarian cancer and borderline tumours were examined, based on data from the population-based Cancer Registry of Norway. Relative risks (RRs) of dying were derived from Cox regression models. Logistic regression analysis on the proportion of cases with a localised tumour was performed. The 5-year relative survival rate of patients with ovarian cancer increased steadily from 1954 to 1993, being most pronounced in women below the age of 65 at the time of diagnosis. No improvement was seen for women older than 75. For all patients with ovarian cancer, an RR of dying of 0.48 (95% CI = 0.44-0.53) was estimated in 1989-1993 compared with 1954-1958. For patients with epithelial cancer, an RR of 0.63 (95% CI = 0.57-0.69) was seen in 1989-1993 compared with 1970-1973. Patients with mucinous, endometrioid and clear cell tumours had the highest odds of having a localised tumour. The age-adjusted 5-year relative survival rate of patients with borderline tumours was almost constant between 1970 and 1993, at about 93%. The prognosis of patients with ovarian cancer in Norway has improved since the 1950s. The very favourable prognosis of patients with borderline tumours has remained unchanged since the 1970s.