Summary.-Macrophages have been isolated from ascitic and collagenase -dispersed tumours from patients undergoing surgery for ovarian cancer. Macrophages were present in varying proportions in both sites, though the ratio of macrophages to tumour cells was higher in ascites. Marked variation in size (as detected by sedimentation velocity) and cytochemical markers in the macrophages was noted. Highly enriched macrophage fractions were isolated from the ascites and collagenasedispersed solid tumours by a combination of sedimentation velocity and selective EA RFC or adherence techniques. Suppressor activity in the PHA assay was detected in tumour macrophages (4/10 giving>50% inhibition), ascitic macrophages (1/15) and blood monocytes (2/7). Lymphocyte fractions from tumours were unresponsive to PHA and failed to suppress the blood response. Suppressor activity was also present in the purified tumour-cell fraction of 6/14 patients.ADCC activity was tested in a few patients. When the activity was determined against the SB target cells, tumour-derived macrophages were inactive, whereas the ascitic fraction showed low but significant activity which averaged much lower than patient blood values. The ADCC assays carried out with the CRC target cell indicated activity within the range of patient blood values in 4/4 ascites and 2/4 tumour macrophage fractions.Cytotoxicity was also assessed against co-purified autologous tumour cells. Although activity was detected in many of the tests, the results seemed to reflect target cell sensitivity. There appeared to be a correlation between cytotoxicity with test macrophages and normal blood mononuclear cells.The results indicate that the cytochemical heterogeneity and the variation in size between macrophage fractions is associated with a spectrum of activities.WE HAVE INITIATED a study of immune competence of the various inflammatory cell types infiltrating primary solid and ascitic ovarian tumours. In the first paper (Haskill et al., 1982a) we outlined the methods used to isolate these cells and characterized the cell markers associated with infiltrating cells from these tumours. Two classes were characterized; 1 sedimented at < 6 mm/h and was similar in size to most blood mononuclear cells; the other was composed of larger, strongly adherent macrophages distinct from blood monocytes, which sedimented with the tumour cells. In the second communication (Haskill et al. 1982b) we investigated effector-cell functions (PHA, ADCC and NK) associated with blood and bloodequivalent inflammatory cells present in both ascitic and solid tumours. The data indicated that all tumour-derived effector-cell tests were markedly depres-