In Drosophila , the Jun amino-terminal kinase (JNK) homolog Basket (Bsk) is required for epidermal closure. Mutants for Src42A , a Drosophila c- src protooncogene homolog, are described. Src42A functions in epidermal closure during both embryogenesis and metamorphosis. The severity of the epidermal closure defect in the Src42A mutant depended on the amount of Bsk activity, and the amount of Bsk activity depended on the amount of Src42A. Thus, activation of the Bsk pathway is required downstream of Src42A in epidermal closure. This work confirms mammalian studies that demonstrated a physiological link between Src and JNK.