Primary ovarian carcinomas of 49 patients have been used to study the relation between microvessel counts and prognosis. All tumours were of the common epithelial type, FIGO 3 or 4, were treated by debulking surgery and cisplatin based chemotherapy. Primary tumour tissue obtained at surgery was embedded in paraffin, cut at 4 microns and stained with Ulex to accentuate the microvessels. The number of microvessels per unit area was counted according to a standardized protocol at a magnification of x 250 in 4 fields, which showed high field (R = 0.98) and acceptable case reproducibility (R = 0.70). Microvessell counts did not show associations with other prognostic variables such as FIGO stage, bulky disease-or-not, differentiation grade, DNA ploidy, volume percentage epithelium, mitotic activity index and mean nuclear area. In survival analysis, a tendency for worse prognosis with higher microvessel counts was found, although statistical significance was not reached (p = 0.25). Correction for volume percentage epithelium did not improve this result. Multivariate survival analysis did not reveal additional prognostic value of microvessel counts to other prognostic factors such as FIGO stage, bulky disease-or-not, volume percentage epithelium, mitotic activity index and mean and SD of nuclear area. In conclusion, although a tendency for worse survival with higher microvessel counts has been found, vascularity does not seem to have a significant impact on survival of adequately debulked advanced ovarian cancer patients treated with cisplatin.