Cytogenetic and molecular responses to standard-dose imatinib (IM) were correlated with trough IM plasma levels for 78 patients with chronic myeloid leukemia (CML) after a minimum of 12 months of IM therapy. The mean trough IM plasma level was 1065 ng/ml (range, 203-2910). There was no correlation of mean plasma trough IM levels and complete cytogenetic response (CCR) at 1 year (CCR 1010 ng/ml vs no CCR 1175 ng/ml P=.29) or major molecular response (MMR) (MMR1067 ng/ml vs no MMR 1063 ng/ml P=.74) after a median of 1298 days of IM therapy. CCR and MMR did correlate with Sokal risk scores with the odds of achieving CCR or MMR for a low risk vs high risk score of 10.8 (95% CI 2.2-53.5) and 6.4 (95% CI 1.4-29.4), respectively. Furthermore, a longer duration of IM therapy also was associated with a greater likelihood of achieving MMR (P=.02).