This study uses a sample of all firms operating in 100 manufacturing industries to examine some aspects of firm dynamics. It finds that firm growth, the variability of firm growth, and the probability that a firm will fail decrease with firm age. It also finds that firm growth decreases at a diminishing rate with firm size even after controlling for the exit of slow-growing firms from the sample. Gibrat's Law therefore fails, although the severity of the failure decreases with firm size. Copyright 1987 by Blackwell Publishing Ltd.