Five annual parasitological surveys and one serological survey, respectively based on the Kato-Katz and free sedimentation methods and the Western blot technique, were conducted in Sumidouro, Rio de Janeiro, Brazil, an endemic county for schistosomiasis. Possible influences of the use of these methodologies on social, cultural, and ethical aspects of the study population were also evaluated. Having the opportunity to choose the different techniques was a conclusive issue influencing participation by the population. Prevalence rates of positive results for stool tests were: 11.6% (1995); 8.8% (1996); 12.2% (1998); 5.9% (1999); and 3.2% (2000). In the period during which the serological survey was performed, the use of laboratory testing in association with analysis of clinical data and available data on transmission and treatment generated a diagnostic procedure termed "coproseroepidemiology". This methodology contributed to significant improvements in the accuracy of measurement of local schistosomiasis prevalence, indicating that epidemiological surveillance could help prevent the recurrence of high prevalence rates. The fact that Biomphalaria glabrata was replaced by Melanoides tuberculata in the main transmission focus contributed to a significant decrease in infection rates.