As antiretroviral treatment (ART) for HIV/AIDS is scaled up globally, information on per-person costs is critical to improve efficiency in service delivery and to maximize coverage and health impact. The objective of this study was to review studies on unit costs for delivery of adult and paediatric ART per patient-year, and prevention of mother-to-child transmission (PMTCT) interventions per mother-infant pair screened or treated, in low- and middle-income countries. A systematic review was conducted of English, French and Spanish publications from 2001 to 2009, reporting empirical costing that accounted for at least antiretroviral (ARV) medicines, laboratory testing and personnel. Expenditures were analysed by country-income level and cost component. All costs were standardized to $US, year 2009 values. Several sensitivity analyses were conducted. Analyses covered 29 eligible, comprehensive, costing studies. In the base case, in low-income countries (LIC), median ART cost per patient-year was $US792 (mean: 839, range: 682-1089); for lower-middle-income countries (LMIC), the median was $US932 (mean: 1246, range: 156-3904); and, for upper-middle-income countries (UMIC), the median was $US1454 (mean: 2783, range: 1230-5667). ARV drugs were the largest component of overall ART costs in all settings (64%, 50% and 47% in LIC, LMIC and UMIC, respectively). Of 26 ART studies, 14 reported the drug regimes used, and only one study explicitly reported second-line treatment costs. The second cost driver was laboratory cost in LIC and LMIC (14% and 20%), and personnel costs in UMIC (26%). Two ART studies specified the types of laboratory tests costed, and three studies specifically included above facility-level personnel costs. Three studies reported detailed PMTCT costs, and three studies reported on paediatric ART. There is a paucity of data on the full unit costs for delivery of ART and PMTCT, particularly for LIC and middle-income countries. Heterogeneity in activities costed, and insufficient detail regarding components included in the costing, hampers standardization of unit cost measures. Evaluation of programme-level unit costs would benefit from international guidance on standardized costing methods, and expenditure categories and definitions. Future work should help elucidate the sources of the large variations in delivery unit costs across settings with similar income and epidemiological characteristics.