Metabolic rates of the ctenophore Beroe ovata within the length range from 0.4 mm (newly hatched larvae) to 60 mm were investigated. At 20degreesC the respiration rates (Q, mug O-2 ind.(-1) h(-1)) of individuals with wet weights (W, mg) less than or greater than 100 mg changed according to the equations Q=0.093W(0.62) and Q=0.016W(0.99), respectively. The weight-specific respiration rate of the juvenile ctenophores with wet body weights of 0.021-100 mg diminished approximately 20-fold (from 0.35 to 0.017 mug O-2 mg(-1) h(-1), respectively), but did not change within the range from 100 to 30,000 mg. The difference in the slope of the regression lines seems to be attributable to the ontogenetic changes in B. ovata metabolism. For the tested temperature range of 10-28degreesC, the mean Q(10) coefficient was equal to 2.17+/-0.5. The basal metabolism of B. ovata narcotised by chloral hydrate was 4.5+/-0.9 times lower than total metabolism. Such a metabolic range is considered to be characteristic of aquatic invertebrates with high levels of locomotory activity.