Black locust trees (Robinia pseudoacaciaL.) of variable age and height were studied in relation to vertical distribution of larval tunnels made by the locust borer,Megacyllene robiniae(Forster), in Maryland. Tunnel concentrations were negatively correlated with height above ground level and with bolt diameter. With greater tree size, attacks were concentrated higher on the main trunks. However, upper extremities of trees of all sizes and ages were lightly attacked.