ABSTRACT Background. Peripheral Neuropathy is commonly seen in HIV infected adults. It is believed that cobalamin lack (as documented in 10-30% of HIV infected population) may partly explain HIV associated peripheral neuropathy. Urine methyl malonic acid (UMMA) in HIV infected patients with and without peripheral neuropathy (PN) was studied to establish this association. Methods. Patients with features of PN (pain/numbness in feet or fingers, loss of coordination, abnormal gaits, loss of joint position sense abnormal muscle tone, power and reflexes and Rombergs sign) were recruited. They were subdivided into groups on ARV and treatment naive. A third arm are those with no PN. Twenty-four hour urine and 5mls of EDTA blood were collected from participants having signed informed consents. Urine Samples of 20 HIV negative participants (10 males and 10 females with no P.N. were also analyzed) UMMA was determined by Cation Exchange High Performance Liquid Chromatography with Ultraviolet detector. Full blood count and CD4 cell count were determined using Sysmex Haematology Autoanalyzer and Partec cyflow respectively. Simple proportions of patients with raised UMMA (defined as value> 3.4mg in 24hrs) were determined for each arm. Differences were compared with chisquare statistics. Results. A total of 206 patients were enrolled but only 165 submitted 24hr urine samples acceptable assay. Of this 165, 118 had PN. 47 had no PN. Raised UMMA was found more commonly 76.6% (36 of 47) in patients with no PN than in those with PN 53.4% (63/118) P 0.018. Of the 118 with PN 26 were treatment naive and 23 (85.5%) of these had raised UMMA whilst 40 (43.5%) of 92 of those on ART had raised UMMA 8 p=0.0009. Whereas the mean CD4 count (344/l) for those on ART is significantly higher than in those that are treatment naive 217/l in the arms with PN there is no significant difference in CD4 of those without peripheral neuropathy when they were subdivided into treatment experienced (295/l) and naive groups (299/l). P=0.9 Similarly, mean values of red cell indices were higher in patients with neuropathy compared with those without neuropathy. The differences reached a significant level in MCH and MCV where neuropathy patients had 30.05pg and 92.43fl respectively. Corresponding values in patients without neuropathy were 28.16pg and 88.65fl. P<0.05 in both cases. Conclusion Findings suggest that cobalamin deficiency (measured by UMMA) even though common in HIV infected patients, may not be the cause of neuropathy in these patients. ART appears to decrease UMMA.