Studies on gastrointestinal parasites and the epidemiology and pathogenesis of blood protozoa in ruminants have been undertaken during the last few years. An abattoir survey for a period of one year showed that most large ruminants slaughtered in the Bogor abattoir were infected with nematodes, about half with trematodes and few with blood parasites. Worm infections were also common in small ruminants but none were infected with blood protozoa. Some field studies on Fasciola infection in large ruminants showed that these animals were susceptible to the disease. The seasonal prevalence of fascioliasis is not yet fully determined; management systems and the local geography play an important role. Most anthelmintics were effective against worm infection in large and small ruminants. A new flukicide (triclabendazole) is highly effective against both immature and mature liver flukes. Studies on the epidemiology and pathogenesis of trypanosomiasis in cattle and buffalo have been conducted since 1982. The results indicate that T. evansi is prevalent in five regions in Java; the prevalence rates are higher in Sahiwal and Belmont Red than Ongole cattle or buffalo. ELISA values increase with increasing age of the animals. Buffaloes are more susceptible than cattle. Naganol is the drug of choice for control of trypanosomiasis in Indonesia.