The complex interactions between the triggering microbe and the defense mechanisms of the host in reactive arthritis have been studied in several laboratories around the world, and interesting observations have been made. Research has also focused on the mediators in the inflammatory process in joints, and these results are helping to slowly build a comprehensive picture about the pathogenetic process in reactive arthritis. For the practicing clinician, some important new findings have emerged. It is known that asymptomatic urogenital infections are quite common as a trigger of reactive arthritis. More aggressive treatment, including disease-modifying drugs as used in the therapy of rheumatoid arthritis, is becoming accepted. The value of antibiotic treatment is being studied, but final conclusions will not be made for perhaps a few years.