A simple method for the isolation of human peripheral blood monocytes in cell suspension is described. The method is based on the adherence and detachment characteristics of monocytes during their in vitro cultivation and does not require any gradient centrifugation or modulating substances. The mean percentage of monocytes recovered from different donors was 81.9% (60-100%) of the original phagocytic cells found in the peripheral blood of the tested donors and the cell suspensions obtained consisted of more than 95% of monocytes. The monocytes isolated in suspensions show high activity in various monocyte functions tested.