Lipase activity of the midgut gland during larval and postlarval stages of Penaeus vannamei was assayed to determine its capability to digest lipids from feed and involvement in digesting lipids from reserves during fasting conditions. Lipase activity was detected at all larval stages, increasing from nauplii to protozoea. Lipase isoenzymes at larval stages were evaluated by SDS-PAGE using 4-methylumbelliferone butyrate as the substrate. Results showed that shrimp larvae possess a nearly complete set of lipases starting with the first larval stage. In addition, to understand the effects of fasting conditions as a stress factor on lipase activity, intermolt shrimp were fasted up to 5 days, a period corresponding to the normal time that shrimp starve during molting, in which they cannot eat. Digestive lipases were affected by fasting, increasing in activity after 24 h of treatment, suggesting that lipid is used as an energy reserve during fasting. Proteins with lipase activity were identified and characterized by zymograms; the presence of more than one lipase enzyme could be one way to hydrolyze triacylglycerides more efficiently as the first step of fat assimilation and to obtain energy from fatty acids under fasting conditions.