The object of the study was to evaluate outcomes of a randomized clinical trial (RCT) of a pharmacist intervention for depressed patients in primary care (PC). We report antidepressant (AD) use and depression severity outcomes at 6-months. The RCT was conducted between 1998 and 2000 in 9 eastern Massachusetts PC practices. We studied 533 patients with major depression and/or dysthymia as determined by a screening test done at the time of a routine PC office visit. The majority of participants had recurrent depressive episodes (63.5% with >/=4 lifetime episodes), and 49.5% were taking AD medications at enrollment. Consultation in person and by telephone was performed by a clinical pharmacist who assisted the primary care practitioner (PCP) and patient in medication choice, dose, and regimen, in accordance with AHCPR depression guidelines. Six-month AD use rates for intervention patients exceeded controls (57.5% vs. 46.2%, P =.03). Furthermore, the intervention was effective in improving AD use rates for patients not on ADs at enrollment (32.3% vs. 10.9%, P =.001). The pharmacist intervention proved equally effective in subgroups traditionally considered difficult to treat: those with chronic depression and dysthymia. Patients taking ADs had better modified Beck Depression Inventory (mBDI) outcomes than patients not taking ADs, (-6.3 points change, vs. -2.8, P =.01) but the outcome differences between intervention and control patients were not statistically significant (17.7 BDI points vs. 19.4 BDI points, P =.16). Pharmacists significantly improved rates of AD use in PC patients, especially for those not on ADs at enrollment, but outcome differences were too small to be statistically significant. Difficult-to-treat subgroups may benefit from pharmacists' care.