We have combined a one-dimensional mixing model with chemical parametes to model distribution of H2O2 in the surface ocean. The shape of the modeled H2O2 depth profile and the shape of the surface-concentration diel were controlled by mixing dynamics. The model reproduced measured mixed-layer H2O2 concentrations, within 20% at six of 14 stations, and within 40% at four other stations. This strongly supported the model's identification of photoproduction, mixing, and removal as the major processes controlling H2O2 distribution in the surface ocean. The key to this performance was identification of two classes of photoproductive waters, based on the ratio of UV absorption (c330 nm m-1) to visible absorption (c460 nm). ¿ American Geophysical Union 1993