The focus of African human trypanosomiasis at Douala was evaluated in 1973 for the last time. The authors report on the results of their prospective survey. The methodology was characterized by utilizing Testryp C.A.T.T. as immunological case finding field test. 11,614 people were surveyed and 5 positive CATT revealed. But such results have be weighted by the rate of people present (52.2%) and by the fact that the selected area was not fully covered. On the other side, the authors examine the operational feasibility of Testryp CATT as immunological case finding field test. Over almost 12,000 tests performed, the feasibility appears very good.