The PACER test is suggested as a field test to estimate maximal oxygen consumption (VO2max) in children. The initial speed of this test concerns teachers with “overweight children” in that this speed requires excessive demands at the start of the test. A modified PACER is proposed starting at a slow initial speed (4.0 km . hr-1) with speed increments (0.5 km . hr-1) to match the original protocol. This study will compare performance in normal weight and overweight 13-14 year old children using both modified PACER and PACER tests and compare predicted VO2max to laboratory measured VO2max. Thirty one boys (mean age = 14.48 +/- 0.33 years) consented to be tested twice in their PE classes and twice in the laboratory. Subjects conducted the 20m shuttle tests while wearing heart rate (HR) monitors in the gymnasium. The laboratory tests consisted of walking and/or running on the treadmill using the same speeds as each PACER trial while measuring HR and VO2. In addition, body mass, height, and five skinfolds were taken. From the subject pool, 15 boys with percent fat >20% were placed into the overweight group. The remainder (n=16) were grouped as normal weight. The final run speeds, max HR, and VO2 in each test were compared by group and test. Independent t-test indicated no significant difference in mean age and height between groups. However the overweight children were significantly (p=0.011) heavier than normal weight children (68.0 +/-14.1 vs. 56.7 +/-6.6 kg). The mean (SD) final speeds for the overweight and normal weight children using the original and modified PACER were 11.07 (0.59), 11.72 (0.89), 11.70 (1.11), and 12.47 (1.38) km . hr-1 respectively. ANOVA indicated no interactions of group and test on final run speed, max heart rate, or VO2. Simple effects indicate a significant (F(1,29)=4.98, p=0.033) group differences and (F(3,87) = 11.58, p<0.01) test differences in final speed. Simple effects indicate significant (F (1,29) = 17.45, P<0.001) group differences in VO2 with the overweight children obtaining lower values than normal weight children (39.40 +/-3.68 ml . kg-1 . min-1 vs. 44.66 +/-4.67 ml . kg-1 . min-1), however no difference between estimated VO2 and actual VO2. No differences were evident in max heart rate. Based upon these findings, there seems to be some advantage for modifying the PACER test to obtain higher final speeds for children however it may not improve the estimation of actual maximal oxygen consumption.Keyword(s): exercise/fitness, measurement/evaluation, youth-at-risk