Screening a population of relatives of current schizophrenic patients could be an efficient means to accrue a sample of early first episode or prodromal patients for a prediction study or an intervention study. The risk of new onset schizophrenia cases in any one year in a population of relatives depends on the number of schizophrenic probands and three additional factors: (1) the age of onset distribution for schizophrenia; (2) the lifetime risk of the at-risk group of relatives selected; and (3) the number of at-risk relatives per proband and their age distribution. Estimates are made for each of these parameters, and calculations are presented. The base model suggests that screening all siblings and children of patients with schizophrenia would yield approximately 19 new cases of schizophrenia per year per 10,000 relatives screened. The results of the calculation are relatively insensitive to reasonable variation of most model parameter estimates. The yield of new cases obtained by screening relatives of current patients appears to be low if the purpose is to recruit a sample for an early intervention study over a relatively short period of time.