To evaluate the cycloplegic effect of mixed eye drops containing 0.5% tropicamide and 0.5% phenylephrine in myopic children, and to determine whether their efficacy was associated with their clinical characteristics. Eighty-one myopic children (age, mean +/- SD, 11.0 +/- 1.5 years; mean spherical equivalent refractive error, -4.27 +/- 1.41 D; range, -1.57 to -8.66 D) were recruited. One drop of Mydrin-P was administered to each eye twice, with an interval of 5 min between. Twenty-five minutes after the second drop, accommodative responses were measured with an open-view autorefractometer, while the subject was encouraged to accommodate by binocularly looking at a Maltese cross located at a distance of 33 cm. The difference between the refractive reading and that obtained with a Maltese cross at 500 cm was regarded as residual accommodation (RA). The repeatability of this measurement was also evaluated. The mean RA was 0.21 +/- 0.29 D (range, -0.31 to 0.99 D). There was no association in RA between the right and left eyes, between RA and age, or between RA and sex, but RA was weakly correlated with refractive error (r = 0.274, P = 0.019). The intersubject difference found in RA can be explained mostly by the extent of repeatability (+/-0.71 D). The insignificant magnitude of RA indicated that the mixed eye drop is an acceptable and useful cycloplegic agent in Japanese schoolchildren with a wide range of myopic refractive errors.