OBJECTIVE To determine the effect of general anesthesia on the accommodative tone in children. METHODS Cohort study in an academic practice. METHODS In children under 12 years of age who were undergoing general anesthesia, cycloplegic refraction was measured using streak retinoscopy during an office visit. Within 6 months, streak retinoscopy without cycloplegia was performed under general anesthesia. The main outcome measure was the difference between retinoscopy under anesthesia and cycloplegic retinoscopy in children. RESULTS In 41 children with an average age of 3.7 years (range, 0.8 to 11 years) retinoscopy under anesthesia yielded significantly more myopic measurements than cycloplegic retinoscopy for the sphere and spherical equivalent (P < 0.0001 for both) but was in good agreement with cycloplegic retinoscopy for cylinder power and axis. The average difference between retinoscopy under anesthesia and cycloplegic retinoscopy was -0.98 diopters (D) (95% limit of agreement, -3.08 D to +1.10 D) for the sphere, 0.08 D (95% limit of agreement, -0.67 D to +0.82 D) for the cylinder, and -0.94 D (95% limit of agreement, -3.01 D to +1.13 D) for the spherical equivalent. Retinoscopy under anesthesia was within 1 D of cycloplegic retinoscopy in 25 subjects (61%) for the sphere, in all subjects for the cylinder, and in 28 subjects (68.3%) for the spherical equivalent. CONCLUSIONS Although general anesthesia reduced the accommodative tone in most children, it was still significant in some as compared to the tone found in cycloplegic retinoscopy. If an accurate measurement is essential, cycloplegia is recommended when measuring refraction in children under general anesthesia.