The glutathione S-transferases (GSTs) are a multi-gene family of enzymes involved in detoxifying electrophilic compounds and the expression of these enzymes in tumours has been proposed as one important mechanism of anti-cancer drug resistance. In this study, the localization of the major cytoplasmic forms of GST has been studied in soft tissue sarcomas by immunohistochemistry. The alpha, mu, and pi forms of GST were identified in 59, 68, and 51 per cent of tumours, respectively. In addition, GST pi immunoreactivity was consistently identified in fibroblasts in adjacent non-neoplastic tissue. The presence of specific forms of GST in soft tissue sarcomas may contribute to the drug resistance frequently observed in these tumours.