The threshold of stereoacuity is reported as measured on 369 normal children aged 3 to 7 years, and on 51 normal adults. Four standard clinical stereotests were used and two different testing procedures adopted. The results show that both threshold and variability decrease with age, and performance becomes adult-like at different ages for different tests. Interest correlations are poor, and in cases where the correlation is significant, no identifiable pattern emerges between testing procedures, age, and stereotests. The procedures themselves gave no significant difference in stereoacuity values between all four tests.