This study investigated the magnitude of the asymmetrical tonic neck reflex (ATNR) response in forty preschool children, grouped by age (3 years and 5 years) and sex. The ATNR response was measured by electrogoniometers at the head and elbows and recorded graphically on an X-Y plotter. Change scores indicating the difference in degrees of elbow flexion before and after head rotation were analyzed. Repetition of the stimulus (head turning) to the left and to the right occurred under two test postures (supine, quadrupedal) with the effect of a blindfold nested within quadruped trials and the effect of added tension nested within supine, totaling 16 trials per child. The magnitude of the ATNR decreased significantly with age, but sex differences were not significant. The quadrupedal test posture produced significant increases in the supine posture. The blindfold did not produce significant main effects. Electrogoniometric measurement consistently demonstrated the magnitude of the ATNR in normal preschool children, which decreases with age, is dependent upon test posture and can provide numerical guides in clinical tests of central nervous system integration.