This is randomised, placebo-controlled, double-blind, parallel-group, multisite, study to demonstrate whether low dose stavudine (d4T) is non-inferior to tenofovir (in terms of both viral suppression and toxicity) to tenofovir (TDF) after 2 years of HIV treatment. If so, this will allow approximately two people requiring antiretrovirals to be treated for the price of one, with the same outcomes at two years. This is of huge public health consequence in Southern Africa, where TDF and zidovudine (AZT) now consume the majority of the antiretroviral budget. Decreasing total drug doses of antiretroviral agents, while maintaining efficacy, represents an untapped possibility for decreasing costs and toxicity, if efficacy can be maintained. Stavudine (d4T), an NRTI, is currently the second most commonly used antiretroviral worldwide in developing countries. Stavudine is an ideal candidate for assessment because of low cost, widespread use, and co-formulation, albeit at a dose that has significant side effects. While well tolerated in the short term, dose-dependent medium and long-term side effects, namely lipoatrophy and peripheral neuropathy, are very common. lipoatrophy is insidious, largely irreversible, and highly stigmatising, These toxicities have lead to the withdrawal of Stavudine as a recommended drug in most countries that can afford an alternative, even in second and subsequent regimens; the World Health Organisation (WHO) recommends that countries, wherever possible, move away from using Stavudine. However, there are data that suggest a lower dose of Stavudine would be better tolerated than the currently recommended dose and will be as effective in suppressing viral load as currently preferred first-line drugs. Consented patients will be randomised into one of two treatment arms using the interactive voice response systems (IVRS). The study monitor will maintain current personal knowledge of the study through observation, review of study records and source documentation, and discussion of the conduct of the study with the principal investigator or sub investigator and staff. Data will be captured onto electronic data capture system and managed for completeness, consistency and accuracy. All study operations such as patient recruitment, data management, safety reporting will be guided by Standard Operating Procedure (SOP) documents. A total of 1068 male and female antiretroviral-naive patients infected with HIV-1 will be randomised in a 1:1 ratio (approximately 534 patients per treatment group) to Treatment Group 1 (d4T/3TC+EFV) or Treatment Group 2 (TDF/3TC+EFV). Approximately 15% of patients are expected not to be evaluable for the PP set, therefore resulting in 907 patients for the PP set. This will provide 90% power to show non-inferiority between the 2 treatment groups for the proportion of patients achieving the primary efficacy endpoint (undetectable plasma HIV-1 RNA levels \[\<50 copies/mL\] at Week 48) for the PP set (and 94% power for the all-randomised set), using a non-inferiority margin of 10% and a 1-sided 2.5 significance level. The proportion of patients achieving the primary efficacy endpoint has been assumed to be 70% in both treatment groups. The sample size calculation has been adjusted to allow for stopping at 2 interim analyses.