We studied the growth of primary schoolchildren with hookworm (87%), T. trichiura (97%), and A. lumbricoides (49%) who received a single 400 mg dose of albendazole or an identical placebo. Children were allocated at random to placebo (PL, n = 72) or albendazole (A, n = 78) groups, treated, and re-examined 6 months later. The A group gained significantly more than the PL group in weight (1.3 kg), percent weight for age (4.5% age points), percent height for age (0.5% age points), percent weight for height (4.3% age points), percent arm circumference (2.9% age points), and in triceps and subscapular skinfold thicknesses (1.2 mm). The PL group showed significant decreases between exams in percent weight for age, percent height for age, percent weight for height, percent arm circumference for age, and skinfold thicknesses for age. The A group had highly significant increases (P < 0.0002) in all of these parameters except height for age. From Exam 1 to 2, the A group exhibited decreases (P < 0.0002) in geometric x̄ eggs per gram of feces (epg): for hookworm, x̄ = 1,183 epg at Exam 1 vs. 136 epg at Exam 2 (67% egg reduction); for T. trichiura, x̄ = 2.857 epg at Exam 1 vs. 1,061 epg at Exam 2 (28% egg reduction); and for A. lumbricoides, x̄ = 86 epg at Exam 1 vs. 2 epg at Exam 2 (91% egg reduction). The PL group had a borderline increase in geometric x̄ hookworm egg count, no significant change in T. trichiura egg count, and a small but significant decrease in A. lumbricoides egg count. Decreases in intensities of all infections were significant predictors of growth improvement. Hookworm egg count entered the equations for all 6 measurements, and A. lumbricoides and T. trichiura entered 4/6 equations. Single dose treatment with albendazole, despite continual exposure to infection, can permit improved growth rates in areas where intestinal helminths and protein-energy malnutrition are highly prevalent.