We describe a method for determination of barbiturates, amphetamines, opiates, and methadone by the "enzyme multiplied immunoassay technique" (EMIT) applied to the centrifugal analyzer. This method gives results that agree well (92% for barbiturates, 97% for opiates, 94% for methadone, and 96% for amphetamines) with those obtained by the same technique with the SyvaGilford EMIT instrumentation. Its advantages include use of half as much of the expensive reagents; capability of batch operation, which removes the need for continual attention; and more nearly complete automation. For individual samples it is as fast as the manual method; for large numbers of specimens it is faster.