Gambian infants show growth faltering, but the underlying body composition is unknown. The present study aimed to compare body composition in Gambian and UK infants using 2H dilution; and to evaluate accuracy of bioelectrical impedance analysis (BIA) and creatinine excretion for estimating lean mass (LM), using 2H as the reference. Body composition was measured in thirty Gambian infants, aged 3–18 months, using (1) anthropometry, (2) 2H, (3) BIA (equation of Fjeld et al.Pediatr Res (1990), 27, 98–102) and (4) 5 h urinary creatinine excretion. Compared with UK reference data, Gambian infants were light, short and had reduced BMI and skinfolds. The subscapular skinfold standard deviation score (SDS) was greater than the triceps SDS (P < 0·01), indicating central fat preservation. Both LM and fat mass were reduced in Gambian infants, with or without adjustment for length. However, whereas the Gambia–UK difference in LM increased with age, that in fat mass decreased. Average creatinine excretion was similar to that expected (95·5 (sd 23·2) % recovery), but LM estimates showed unacceptable error in individuals. BIA using Fjeld's equation overestimated total body water and LM (P < 0·001), hence a new equation was developed, with standard error of 0·47 kg LM. In conclusion, Gambian infants characterised by growth faltering had LM deficits that increased with age. However, adiposity increased with age, and showed indications of a more central distribution than in the reference infants. A new BIA equation for LM prediction is presented; however, creatinine excretion is not recommended for LM estimation in this population.