An improved enzymatic fluorometric method for automated analysis of lactate in perchloric acid extracts of capillary blood with flow injection (FIA) is described. The concentrations of lactate can be measured in as little as 20 µl capillary blood from an exercising person. Within-day and between-day coefficients of variation are about 2%. The recovery of lactate from whole blood is 101%. Lactate is stable in perchloric acid extracts for at least 15 days at room temperature, and at +4°C at least 30 days. Blank fluorescence in perchloric acid extracts of blood is low with the improved method. The FIA system is simple to use, inexpensive to operate, and is recommended for any laboratory with a high throughput of samples.