Twenty-five infants born to methadone-dependent mothers were studied between 6 and 41 months of age for growth, developmental, behavioral and neurological status. Fifty infants of non-drug-dependent mothers of similar socio-economic backgrounds served as controls. Weight was<3rd percentile in 8% of methadone infants and 2.6% of controls(p=0.10)while 26% of methadone infants were < 3rd percentile in height in contrast to none in the control group(p<0.001). Head circumferences were all with ± 2 S D. Gesell's developmental schedule showed a mean D.Q. in the study group of 100 (S D ± 8.8)and in the control group 102(S D ± 10.5). There was no significant difference in gross and fine motor, adaptive, personal-social and language behavior between the two groups. Behavior profiles were scored by assigning grades 1 (decreased) to 5 (increased behavior). In the methadone group there was a marked shift toward high scores; the control group profiles were normal. This behavior pattern decreased in intensity and frequency as the children reached 2 years of age. Neurologic examinations were all normal. In conclusion, children born to methadone-dependent mothers as compared to controls show: decreased linear growth under 3½ years of age, behavior characterized by increased activity and intensity of response in the first 18 months of life, and no differences with regard to developmental and neurological status.