Antiretroviral treatment (ART) has been available in the private sector in Namibia since 1998. National guidelines were developed by the Ministry of Health and clinicians of the public and private sector in 2003 and launched at the start of the public sector ART programme by the Ministry of Health. The Namibian HIV Clinicians Society was established around this period to promote adherence to the national guidelines and to provide comprehensive training for health professionals. To monitor adherence to national ART guidelines, in 2003, the Society requested access to anonymized data on ART dispensing from the medical insurance industry. Dispensing data from all Namibian medical insurance companies were obtained. ART regimens were categorized as recommended (non-nucleoside reverse transcriptase inhibitor-based and boosted protease inhibitor [PI]-based), not recommended (non-boosted PI-based or stavudine/didanosine-containing regimens), ineffective (dual therapy) and second line or salvage regimens. This analysis was repeated in 2004, 2005 and 2008. In 2003, only 2306 adult private patients received ART, of which only 1527 (66%) were recommended regimens. In 2008, 7010 private patients received ART, of which 6372 (91%) were recommended regimens. The private sector covered about 15% of the total number of 46,732 reported ART patients reported in the year 2008. Many of these private patients might not have accessed ART in the public sector.