OBJECTIVE To compare cervical range of motion values following active (nonpractitioner-assisted) vs. passive (practitioner-assisted) movement of the head to end range. METHODS Randomized, double-blind, within-subject comparisons. METHODS Cervical Ergonomics Laboratory, Palmer College of Chiropractic-West, Sunnyvale, CA. METHODS Pain-free chiropractic college students, nearly evenly divided with respect to gender and ranging from 22-38 yr of age, were used in the study. Subjects exhibiting goniometrically determined cervical lateral-flexion or rotational passive end-range asymmetries of 10 degrees or greater were selected for experimentation. METHODS None. METHODS A goniometric (inclinometric) device was used for active and passive cervical end-range assessments. Active assessments were performed first, followed immediately by passive assessments in each subject. RESULTS Results demonstrated that the magnitudes of end-range asymmetry detected following active assessment were only about half of those observed following passive assessments. Moreover, whereas active end-range values were about 5 degrees less than passive on the most restricted side of passive movement, active end-range values were about 10 degrees less than passive on the least restricted side of passive end range. CONCLUSIONS These results are consistent with the notion that cortical influences mediating active movement are rather intolerant of asymmetric states involving end-range capability. This results in compensatory reductions in active movement on the side of greatest potential passive end range, thereby acting to preserve symmetry at the expense of overall range of motion. Results also suggest that measures obtained following active movement may be far more difficult to interpret than those obtained following passive assessments, particularly when information regarding possible asymmetry of end-range capability is considered to be of primary clinical and/or experimental importance.