The major part of Venezuela oil production is located in and around the Lake Maracaibo Basin. The samples were collected over a 1-year period at Catatumbo and La Esperanza sites. The rainwater was acidic, with a VWA-pH of 4.6 for Catatumbo and 4.2 for La Esperanza. This acidity is made up in 93% by inorganic acids (mainly H2SO4), and NH4+ is the major cation which buffer the acidity of precipitation. An excess of sulfate (SO2*) > 96% was obtained in both sites. Correlation analysis shows that H+ is strongly correlated with SO4x. Anthropogenic air pollution from oil fields (H2S) and the burning of sulphur-bearing fuels (SO2) are probably the dominant sources; however, the lack of correlation between the H+ and NO3− levels would appear to indicate that the SO4* is also of biogenic origin (H2S-DMS from Sinamaica Lagoon-Lake Maracaibo- and the Caribbean). Statistical analysis of the pooled data indicated that the concentration differences between Catatumbo and La Esperanza sites are not significant at 99% confidence level.