del(20q) can be observed in hematologic neoplasms, including chronic myelogenous leukemia (CML), and has been reported in patients undergoing blast transformation. We describe 10 patients with CML in hematologic and cytogenetic remission with del(20q) detected by conventional cytogenetics. There were 6 men and 4 women with a median age of 56 years. All patients initially had BCR-ABL1 and t(9;22) (q34;q11.2) and achieved morphologic and cytogenetic remission after therapy. del(20q) was identified before (2/10 [20%]), at the time of (3/10 [30%]), or after (5/10 [50%]) cytogenetic remission and was not associated with morphologic evidence of dysplasia. At last follow-up, no patients had a myelodysplastic syndrome (MDS). Leukocyte and platelet counts were normal; 4 of 10 patients had mild anemia. Nine patients have remained in morphologic and cytogenetic remission with stable del(20q). BCR-ABL1 fusion transcript levels were absent or low (median, 0.01%). Recently, in 1 patient, recurrent CML developed and del(20q) was lost. We conclude that del(20q) in the setting of CML in remission is not predictive of MDS or blast transformation.