Prologue THE INTRAFAMILIAL TRANSMISSION OF

THE SET of seven papers which follow constitutes a report which in its design comple-ments the more common type of clinical investigation. The study sets out specifically to examine a pair of hypotheses: that rheumatoid arthritis is in part determined by a genetic mechanism and is in part determined by social effects within the family. The study uses a carefully validated and thrice repeated interview to classify people with regard to rheumatoid arthritis. This interview technique is essential for it would be quite impossible to examine the widely distributed relatives of a national sample of arthritics. The experimental design compares the frequency of rheumatoid arthritis in first degree relatives, who share one half of their genes with the key persons with arthritis, with the frequency in second degree relatives, who share one eighth of their genes, and with the frequency in unrelated persons, who share only a negligible percentage of their genes. The study also tackles the psychological side of rheumatoid arthritis with quantitative measuring instruments. The results of the studies upport the findings in the clinical literature which are well summarized in a book not widely enoug