Fetal body movements were studied in three groups of gravid rhesus macaques fed different amounts of dietary zinc (100 micrograms Zn/g diet, control, n = 12; 4 micrograms Zn/g diet, marginal deprivation, n = 7; 2 micrograms Zn/g diet, moderate deprivation, n = 11). Sonographic examinations were conducted during the third trimester in awake chair-restrained dams. Movement categories, derived from the human biophysical profile, were motor activity (trunk and limb movements), startle, and breathing movements. Moderately deprived fetuses were more active than controls on gestational day (GD) 115; maternal plasma zinc concentrations were significantly correlated with fetal activity at this time. In addition moderately deprived fetuses exhibited fewer breathing episodes on GDs 115-135. Biometrics measures indicated growth retardation in one moderately deprived fetus. These data suggest that moderate, but not marginal, dietary zinc deprivation influences fetal status as evaluated by sonography.