This paper reports on the importance of firm entry and growth flows in Portuguese manufacturing during the period 1982–86, and investigates their determinants. We find that both movements are induced by past profitability and deterred by economies of scale, product differentiation and sunk costs. The analysis does not reject the hypothesis that the determinants of firm entry and growth are quantitatively the same, thereby giving some support to the hypothesis that entry and expansion are close substitutes in absorbing industry excess profits, and that the choice between them does not depend on the height of the entry/mobility barriers.