Using cell-fractionation techniques (differential and discontinuous gradient centrifugation), we obtained a highly enriched fraction containing the Golgi complex of Tritrichomonas foetus. This fraction was further subfractionated by sodium carbonate (150 mM) treatment at pH 11.5, leading to the isolation of the Golgi content and membrane subfractions. Both fractions were characterized by electron microscopy. The protein content of membrane and luminal subfractions was about 40% and 60% of the total Golgi protein, respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed an enrichment of 15 protein bands in the Golgi fraction, with molecular masses varying between 15 and 116 kDa. Alkaline treatment released some proteins into the medium, but most of them were associated with the Golgi membrane.