Twenty-six offspring representative of 9 families with Huntington's chorea in the immediate ancestry were subjected to the following studies: physical, neurological, psychiatric, psychometric, anthropometric, genetic, and electroencephalographic. Of these various procedures, but 2 seemed to offer probable predictive value: namely, the EEG and the blood groupings. Nineteen, (73.1%) of the subjects showed definite electroencephalographic abnormalities, particularly in the motor regions. Bilateral paroxysmal bursts like those observed in epilepsy were found in the resting record of about half (8) of the cases showing abnormal EEGs. According to a composite weight, 12 offspring had the highest electroencephalographic abnormality and were thought likely to develop the disease as this proportion approximated the genetic probability. No definite intra- or inter-family, or parent-offspring, electroencephalographic resemblances were noted. The study of blood groupings was expanded to include all available cases of Huntington's chorea in addition to the offspring study and disclosed a disproportionately large number of individuals in Groups A and O. Longrange follow-ups with repeated EEGs on a larger series of offspring are recommended as well as a much more extensive examination of the blood groupings of Huntington's chorea patients and their offspring in order to establish the statistical validity of the 2 procedures.