To determine the effect of large and sudden increases in training volume on performance characteristics and the feasibility of using overtraining syndrome symptoms to monitor performance changes, 15 elite judo athletes were examined through 10 wk of training. Athletes performed their regular regimens of resistance (3 d.wk-1), interval (2 d.wk-1), and judo (5 d.wk-1) training in weeks 1-4. Interval and resistance training volumes increased by 50% in weeks 4-8 and returned to baseline in weeks 9-10. Judo training volume was unchanged in weeks 1-8 but increased by 100% in weeks 9-10. Assessments were made in weeks 2, 4, 8, and 10. Isokinetic strength of elbow and knee extensors and flexors increased significantly from weeks 2 to 4 (3-13%), was unchanged from weeks 4 to 8, and decreased significantly (6-12%) from weeks 4 to 10. Total time for 3 x 300 m intervals increased (P less than 0.05) between weeks 2 and 4 and between weeks 4 and 8, while total time for 5 x 50 m sprints decreased (P less than 0.05) from weeks 8 to 10 (less than 2%). Body fat percentage decreased (P less than 0.05) from weeks 2 to 10. Body weight, submaximal and maximal aerobic power, resting (sleeping) systolic and diastolic pressures, resting (sleeping) submaximal and maximal heart rates, exercising blood lactate levels, and vertical jump performance did not change significantly with increases in training volume. These results suggest that 6 wk of overtraining may affect some but not all aspects of performance and that performance may be affected before symptoms of the overtraining syndrome appear.