The plate-fin heat exchanger is normally designed with the assumption that the fluid is uniformly divided among all the parallel passages. In practice, however, the design of the exchanger, the heat transfer process, the operation of the external system, etc., may create high flow maldistribution. The performance deterioration of plate-fin heat exchangers due to flow maldistribution may be serious. In this review, the flow distribution performance in a plate-fin heat exchanger has been experimentally studied and the distribution performance of different distributors' inlet angles has been measured. The combined effects of the inlet angle and mass flow rate on flow maldistribution have been studied. The study is useful in the optimum design of plate-fin heat exchangers.