During the past decade there has been an increasing awareness of the need for a different approach to the problem of bilharziasis. We do know that 180-200 million people are infected and that the infection is increasing but we have not as yet been able to answer the question: Are they suffering from a disease. Study of vital statistics or hospital records, mass biochemical or immunological tests and community surveys have not yet provided the full answer. Gradually and perhaps begrudgingly, we have come to realize that we must study the man- initially by means of well controlled clinical...