“…Suppression of normal CFU-C by myeloid leukaemic cells by conditioned media or by extracts has been shown by some (Chiyoda et al, 1975(Chiyoda et al, , 1976Craddock et al, 1978;Gordon et al, 1978;Knudtson & Mortenson, 1976;Morris et al, 1975) and not by others (Bull et al, 1973;Greenberg et al, 1971;Robinson et al, 1971). We report here further experiments to try…”