Normal human lymphocytes and lymphocytes circulating in 3 patients with chronic lymphocytic leukaemia (CLL-lymphocytes) were freshly isolated from defibrinated blood. Suspensions were frozen, stored at -196 °C and subsequently thawed under specified conditions known to preserve well several aspects of behaviour in vitro. Electron microscopy following short-term culture showed no qualitative differences in ultrastructure between normal lymphocytes and abnormal CLL-lymphocytes either before freezing or after this freezing and thawing procedure. Microtubules were found in all types of cell.