Parasitological diagnosis of Trypanosoma evansi infection in camels is hampered by the small number of parasites in blood circulation, coupled with the tendency of this trypanosome to invade tissues. To overcome this, a more sensitive assay, an antigen enzyme-linked immunosorbent assay (ELISA), was developed, capable of detecting trypanosome antigens released into the bloodstream by dying parasites. To evaluate the usefulness of this assay in assisting chemotherapy, an experiment was designed to compare the ability of a Trypanozoon subgenus-specific monoclonal antibody (TR7) to capture antigens in whole blood and serum of camels in a T. evansi-endemic area of the Marsabit district in northern Kenya. The tests were performed in polystyrene tubes coated with TR7. Antigen ELISA using whole blood was performed in the field, while serum collected on the same day from the same animals was stored at -20 degrees C and tested in the laboratory at a later date. A total of 100 camels were examined. Twelve per cent of the camels were found to be antigenaemic when whole blood was tested, compared to thirteen per cent detected using serum. Thus, the results obtained so far do not show a significant difference in the sensitivity of tube ELISA when detecting antigens either in whole blood or serum.