Changes in protein and carbohydrate content during larval development of Lytechinus variegatus were measured under two diet conditions, low concentration (600 algal cells ml⁻¹ day⁻¹) and high concentration (6,000 algal cells ml⁻¹ day⁻¹) to determine the larval stage at which these proximate constituents showed significant changes under different conditions of food availability. In terms of morphology, larvae under the high concentration diet developed fully and metamorphosed after 30 days, whereas under the low concentration diet, some larvae developed up to the 4 arm stage, and some ceased to develop at the 8 arm stage. No significant differences were found in the percentage of larval survival up to day 24 with both treatments (high: 77 ± 18%, low: 66 ± 24%). With the high concentration diet, protein and carbohydrate content per larvae remained relatively constant through day 17 after fertilization, through the 8-arm stage, and then significantly increased by day 20 coinciding with the first appearance of the rudiment stage, remaining high by day 24, coinciding with the first appearance of pedicellariae. Despite the morphological differences between the larvae at both treatments, no significant differences were found in the protein and carbohydrate content per larvae up to day 24. During normal development with a high concentration diet, growth of the pluteus larva seems to be primarily an increase in dimension of the feeding structures, the arms, that requires little production. After full feeding capacity is reached at the 8-arm stage, production increases with development of the rudiment and the pedicellariae.