RESUMEN
As a sequence to a cross-sectional study on the clinical gradient of the disease by Pesigan et al., (1965) a follow-up of the subjects in that study was made after 12 years. Of the 135 untreated cases followed up, 23 (17.04%) died from various causes of which 12 (8.89%) had signs and symptoms attributable to schistosomiasis as the immediate cause or one of the main causes of death. This occurred in 1 to 11 years with an average of 5 years, which corresponds roughly to 1.78% of the infected cases per year. This is considered a conservative estimate because in the other deaths due to other diseases, schistosomiasis is a contributory cause. A diminishing severity of the disease was observed among the surviving patients which could imply that they must have developed some degree of immunity to the disease.