We conducted a retrospective chart review of antiretroviral therapy (ART) clinic patients treated during the first 12 months after clinics opened in rural Zambia and assessed adherence based on clinic attendance, patient report, and staff assessment. We identified 255 eligible patients (mean age, 39.7 years; 44.3% male; 56.5% married; and 45.5% with only primary school education). Twenty percent had partners known to be HIV positive. Twenty percent were widowed. Thirty-seven percent had disclosed their HIV status to their spouse. Disclosure was less likely among women (27.5% versus 49.6%, P = 0.0005); 36.5% had "clinic buddies" to provide adherence support. Adherence rates were good for 59.2%. Disclosure of HIV status to ones' spouse (P = 0.047), knowing spouses' HIV status (P = 0.02), and having a clinic buddy (P = 0.01) were associated with good adherence. Social support is a key patient-level resource impacting ART adherence in rural Zambia. Limited spousal disclosure affects women more than men. Clinic buddies are associated with better adherence.