OH and OH2 data collected on NASA's Pacific Exploratory Mission-Tropics B (PEM-Tropics B) are presented here and compared to results from a photochemical box model. PEM-Tropics B took place in the tropical Pacific in March and April of 1999 and examined photochemistry and sulfur chemistry in the remote tropical atmosphere. Altitude-resolved HOx budgets are presented. The model showed good overall agreement with the data, with a mean model to observed ratio of 0.86 for OH and 1.03 for HO2. The model tends to underpredict OH at higher altitudes and overpredict at low altitudes. The model agrees well with the HO2 observations at middle altitudes but tends to overpredict slightly at high and low altitudes. ¿ 2001 American Geophysical Union