The visual acuity of 104 patients who had previously been successfully treated for unilateral amblyopia by occlusion of the good eye was examined 6.4 years, on average, after cessation of treatment. Three age groups were defined, according to the age at which treatment was started: younger (2 to 5.5 years), middle (5.5 to 8 years) and older (above 8 years). In 55% of the patients, the long-term follow-up examination revealed deterioration of the visual acuity. In patients in whom amblyopia had been monitored at least up to the age of 9 years, the age at which treatment was started did not significantly affect the mean amount of deterioration or the mean visual acuity noted at the long-term follow-up examination.