Groups of 10 high, 20 above average, and 20 low creative ability subjects were constituted by interjudge agreement from among an adult population who were removed from their biological parents and adopted shortly after birth. The adoptees thus received prebirth influence from their biological relatives and postbirth influence from then: adoptive relatives The rates of recorded mental illness were determined among the adoptees, their biological parents and siblings, and their adoptive parents and siblings Mental illness rates in the adoptees were positively and significantly related to their creative ability level, substantiating the hypothesized relationship between creative ability and mental illness. The mental illness rates of the biological parents were positively and significantly related to the creative ability level of the adoptees. Mental illness rates among the adoptive parents and the adoptive and biological siblings were independent of the adoptees’ creative ability level. The data were interpreted as evidence for the influence of prebirth factors on the relationship between creative ability and mental illness No evidence of family-related postbirth influence was found An evaluation of mental illness rates among uncooperative (nonresponding) potential subjects and their relatives suggested that noncooperation by these adoptees produced a dampening effect on the results of the study.