Bananas were dipped in aqueous solutions of 2,4-dichlorophenoxyacetic acid (2,4-D) or indoleacetic acid (IAA) at concentrations ranging from 10-5 to 10-2M. Auxin, in proportion to its concentration, stimulated ethylene production; 10-2M and 1O-3M IAA and all 2,4-D concentrations advanced ripening relative to control fruit. 2,4-D at concentrations of 10-2M, 10-3M, and sometimes 10-4M stimulated the respiratory climacteric immediately after treatment, but ripening of the peel was delayed compared to the pulp.