Fourteen boys who were exposed to opiates in-utero maintained their index finger in a static, weight-forced position while attempting to maintain a stylus at a fix point producing intentional microtremors. After 2.5 minutes, significant increases in tremor were recorded in mean peak (6 Hz) amplitude while accuracy of sustaining this response was significantly reduced. Age matched boys (ages 7-12) who were raised in an environment in which drugs were used but were not directly exposed in-utero (lifestyle group N=13) or a standard control group (N=12), did not show similar changes over time. Resting or postural-extended tremor did differ among groups. Alcohol, marijuana, or tobacco use by the mother or birth weight of the child did not predict subsequent group differences in tremor. Both biological and environmental variables plus type and sensitivity of measurement used are critical elements for describing long-term, potential residual drug effects in children, especially as they relate to sustained attention. Table, figures, references