INTRODUCTION: This study analyzed the performance of the Kato Katz technique in detecting intestinal schistosomiasis in the State of Pará. METHODS: Of three stool samples provided by each of 380 participants, a total of 16 Kato Katz slides were examined to define the reference value (RV) of positives for comparisons. RESULTS: The RV revealed 37 (9.7%) infected participants in contrast to 10 (2.6%) according to a single slide. CONCLUSIONS: This significant underestimation of the infection rate gives reason to discuss if the current classification of prevalence levels reflects the real situation, principally in low transmission areas, like the Amazon region.