12 females and 60 males (mean ages 13.5 and 15.1 yrs, respectively), who represented the top 1% of the extremely bright students identified by the Study of Mathematically Precocious Youth (C. P. Benbow and J. C. Stanley (see PA, Vol 66:10019)) were tested along with their parents, using a battery of specifically designed cognitive tests. These students represented the top 0.03% of their age group in intellectual ability. Results show that the parents were extremely able and resembled one another significantly more than parents in the general population. In addition, the intellectually precocious children resembled their parents to a lesser extent than children of average ability resemble their parents. These data suggest that considerable assortative mating has occurred among the parents of these extremely gifted youth, but that extreme giftedness cannot be predicted reliably solely as a result of the mating of bright parents.