The degree of practice effects with the Brief NIMH Neuropsychological Battery for HN Infection and AIDS is reported using a 7-10 day test-retest interval. The patient groups were asymptomatic and symptomatic of HN while the control group was made up of ''at risk'' volunteers. Statistically significant practice effects were obtained on the California Verbal Learning Test, the Paced Auditory Serial Addition Task and the Visual Search Test among the infected individuals. The controls subjects demonstrated statistically significant practice effects on all of the neuropsychological tasks. The implications of these findings in prospective studies are discussed.