This study compared the latency of pattern reversal visual evoked potentials (VEP) of 36-month old children exposed to opioid pharmacotherapy in utero to that of a group of non-exposed children. Pregnant women were enrolled as part of an open-label non-randomised flexible dosing longitudinal study. Participants were 21 children whose mothers were treated with buprenorphine- (n= 11) or methadone-pharmacotherapy (n= 10) during pregnancy, and 15 children not exposed to opioids in pregnancy. One-way between groups analyses of variance (ANOVA) were conducted to test the statistical significance of differences between the mean latencies of the peak response to two different sized checkerboard patterns (48' and 69' of retinal arc). Standard multiple regression analyses were conducted to determine whether there was a significant relationship between group status and VEP latencies after adjusting for the effect of covariates. VEP latencies ranged from 98 to 112 milliseconds (ms) for checks of 48' arc, and from 95 to 113 ms for checks of 69' arc. Latencies were comparable across groups. After adjusting for covariates children prenatally exposed to methadone or buprenorphine did not differ significantly from non-opioid exposed children in their responses to either check size. Nor were there any significant differences in VEP latencies between children prenatally exposed to methadone and children prenatally exposed to buprenorphine. Head circumference (HC) was significantly associated with P100 latencies for both check sizes. Data from this controlled, non-randomised study suggest that neither buprenorphine nor methadone appear to have any long-term effects on visual maturity assessed at 36 months of age.