Background Scaling up of antiretroviral therapy in low-resource countries is done on the basis of decentralised, integrated HIV care in rural facilities; however, laboratory monitoring is generally unavailable. We aimed to assess the effectiveness and safety of clinical monitoring alone (CLIN) in terms of non-inferiority to laboratory and clinical monitoring (LAB). Methods We did a randomised, open-label, non-inferiority trial in nine rural district hospitals in Cameroon. Eligible participants were adults (>= 18 years) infected with HIV-1 group M (WHO disease stage 3-4) who had not previously received antiretroviral therapy, and were followed-up for 2 years by health-care workers in routine activities. We randomly assigned participants (1:1) to CLIN or LAB (counts of HIV viral load and CD4 cell every 6 months) groups with a computer-generated list. The primary outcome was non-inferiority of CLIN to LAB in terms of increase in CD4 cell count with a non-inferiority margin of 25%. We did all analyses in participants who attended at least one follow-up visit. This trial is registered with ClinicalTrials.gov, number NCT00301561. Findings 238 (93%) of 256 participants assigned to CLIN and 221 (93%) of 237 assigned to LAB were eligible for analysis. CLIN was not non-inferior to LAB; the mean increase in CD4 cell count was 175 cells per mu L (SD 190, 95% CI 151-200) with CLIN and 206 (190,181-231) with LAB (difference 31 [-63 to 2] and non-inferiority margin -52 [-58 to -45]). Furthermore, in the predefined secondary outcome of treatment changes, 13 participants (6%) in the LAB group switched to second-line regimens whereas no participants in the CLIN group did so (p<0.0001). By contrast, other predefined secondary outcomes were much the same in both groups viral suppression (<40 copies per mL; 465 [49%] of 952 measurements in CLIN vs 456 [52%] of 884 in LAB), HIV resistance (23 [10%] of 238 participants vs 22 [10%] of 219 participants), mortality (44 [18%] of 238 vs 32 [14%] of 221), disease progression (85 [36%] of 238 vs 64 [29%] of 221), adherence (672 [63%] of 1067 measurements vs 621 [61%] of 1011), loss to follow-up (21[9%] of 238 vs 17 [8%] of 221), and toxic effects (46 [19%] of 238 vs 56 [25%] of 221). Interpretation Our findings support WHO's recommendation for laboratory monitoring of antiretroviral therapy. However, the small differences that we noted between the strategies suggest that clinical monitoring alone could be used, at least temporarily, to expand antiretroviral therapy in low-resource settings.