Objectives: The aim of the study was to determine the prevalence of depression among HIV/AIDS patients in Aminu Kano Teaching Hospital (AKTH). A second aim was to determine the socio-demographic, medical and psycho-social factors associated with depression in HIV/AIDS patients at AKTH. Design: The study was a descriptive cross sectional study. Setting: Aminu Kano Teaching Hospital (AKTH), North-western Nigeria. Subjects: Two hundred and fifty patients were selected using systematic sampling methods from all the patients attending the HIV/AIDS clinic of by the Department of Internal Medicine of the hospital. The study was conducted over a period of 6 months (May-October) in 2006. Methods: The socio-demographic data was collected using a structured pretested questionnaire. Thereafter, Hospital Anxiety and Depression scale (HAD) questionnaire was administered to the respondents to screen for depression. Those who scored 8 and above on the HAD scale were assessed for depression using Composite International Diagnostic Interview(CIDI).Severity of the depression of was rated into mild, moderate and severe using CIDI and Hamilton Dpression Rating scale (HDRS). Results: The prevalence of depression among HIV/AIDS patients in Aminu Kano Teaching Hospital Kano was 35%.Using the CIDI further categorized the patients into mild depression 60.9(70%), moderate depression 25.23(29%) and severe depression 0.87(1%). More patients with depression had a past history of psychiatric illness compared to those without depression (p=0.04). Perception of the illness and feelings of stigma showed significant difference in depressed and non-depressed subjects (p=0.00, p=0.00 respectively). The proportion of patients with job problems significantly differed in the two group studied (p=0.00). There were more sexual and educational problems in HIV/AIDS patients with depression compared to those without depression (p=0.00, p=0.00 respectively). Problem with the opposite sex (regression co-efficient =2.1787) and patients’ perception of illness (regression co-efficient =3.2517) were found to be significant predictors of depression. The mean CD4 counts at diagnosis and at present were significantly lower in HIV/AIDS patients with depression compared to the non-depressed HIV/AIDS patients (p=0.00, p=0.01 respectively). Only 6(6.9%) of the 87 depressed patients were identified as having depression by the attending physicians at the HIV/AIDS clinic. Conclusion: The prevalence of depression among HIV/AIDS patients in AKTH was 35%, majority of who were unidentified and untreated by attending physicians.