Lymphokines (LCL-LK) prepared from the human lymphoid cell line RPMI 1788 were injected into dermal nodular metastases of three patients with advanced breast carcinoma anergic to recall antigen (tuberculin). Three different injection schedules were employed. Ten such nodules were examined by excision biopsy and their histological appearances were compared with biopsies of four further nodules not injected with the lymphokine. Intranodular injection of LCL-LK resulted in clinical regression of tumour and histological evidence of tumour-cell necrosis with pleomorphic leucocytic infiltration by polymorphs, macrophages and lymphocytes. Electron microscopy of two such nodules failed to show close cell contact between leucocytes and tumour cells prior to tumour-cell necrosis. This study extends evidence that injection of inflammatory lymphokines into accessible tumour can result in local tumour regression and it suggests that such tumour-cell destruction may be the result of a variety of factors operating during local inflammatory response.