Fifty-three K562-clones were tested against three monoclonal anti-K562-antibodies (MoAbs). The individual NK-cell sensitivity of thirty-one K562-clones was evaluated simultaneously. It was found that considerable differences exist in the antibody binding between single clones and the parental cell line indicating antigenic heterogeneity in the K562 line. Some K562-clones showed increased NK-cell sensitivity in comparison with the uncloned cell line. However, no correlation was observed between both investigated parameters.