The authors investigated lactic anaerobic metabolism in handball players during practice games. Seven players aged 18-21, belonging to second division league clubs, took part in the study. In the laboratory, VO2 max and the onset of blood lactate accumulation (OBLA) were determined with progressive maximal ergocycle tests. On the field, video recordings, cardiotelemetry, and rectal temperature measurements made during the first half of the game were used to quantify exertion. An intravenous catheter worn permanently was used to draw blood for lactate measurements at the 5th, 10th, 15th, 20th, and 30th min of play and after a 10-min rest period. The results confirmed earlier observations showing the need for an excellent maximal aerobic power and capacity in handballers. However, the maximal lactate levels observed (4-9 mmol X l-1) were above those that could be expected from samples drawn only at the end of play. These findings indicate that players must be trained to tolerate high lactate levels to preserve their maximal efficiency throughout the game. Finally, lactate production increased with player exertion and with increasing OBLA.