The simultaneous measurements of atmospheric HCOOH, CH3COOH, H2O2, organic peroxides, HCHO, CH3CHO and isoprene made in the Venezuelan savannah region, in the wet season (September, 1993) and during the period of high solar irradiation is reported. The average concentrations (in ppbv) between 10:00 and 16:00 were: HCOOH 0.75¿0.32, CH3COOH 0.56¿0.28, H2O2 1.37¿0.48, the total peroxides 1.83¿0.60, HCHO 1.38¿0.43, CH3CHO 0.35¿0.15, and isoprene 2.18¿0.78. A good correlation was observed between the concentrations (15 min averages) of both acids. The acids also correlate with isoprene (the most abundant olefin in the savannah atmosphere), H2O2 and the total peroxides. HCOOH also correlates well with HCHO and CH3CHO. These results support the hypothesis that significant amount of formic and acetic acids are produced in the tropical atmosphere as a result of the oxidation of reactive hydrocarbons. ¿ American Geophysical Union 1996