Of 72 patients with chronic myelogenous leukemia (CML), 37 were Ph1 positive, eight were negative, and 27 were not evaluated for the Ph1 chromosome. Of the 37 patients positive for Ph1, 31 had adequate evaluation. These 31 patients were reviewed for survival with reference to spleen size. Seventeen patients with spleens 3 cm or less below the left costal margin had a 50% survival of 75 months, with a mean survival of 53.9 months. Fourteen patients with spleens greater than 3 cm below the left costal margin had a 50% survival of 21 months, with a mean survival of 19 months (P = .0014). It is concluded that small splenic size in CML is associated with longer survival. It may be that this observation should be taken into consideration when considering splenectomy in the management of patients with CML.