Longitudinal and observational studies have provided important information on the course of rheumatoid arthritis (RA), clinical outcomes, and prognostic markers. In terms of clinical effectiveness of drugs used in RA, the results of such projects can be used to complement those of randomized studies. If well designed and conducted, inception cohorts are the most robust types of observational studies, reflect the most complete spectrum of disease, and provide the most reliable prognostic markers for the management of this chronic condition.