Beach cusps develop along seaward faces of growing berms. They appear early in the transitional period of decreasing wave energy from winter- to summer-beach conditions. Growth stages are described and related to currents within the swash zone. Cusp spacing depends on coastal exposure and state of the sea. Conditions under which cusps disappear are described. Although most steps in the depositional development and erosional removal of cusps are understood, the theory of their origin will remain incomplete until the reasons for their spacing are known in quantitative terms.