To develop and apply a model that allows prediction of current and future supply and demand for rheumatology services in the US. A supply model was developed using the age and sex distribution of current physicians, retirement and mortality rates, the number of fellowship slots and fill rates, and practice patterns of rheumatologists. A Markov projection model was used to project needs in 5-year increments from 2005 to 2025. The number of rheumatologists for adult patients in the US in 2005 is 4,946. Male and female rheumatologists are equally distributed up to age 44; above age 44, men predominate. The percent of women in adult rheumatology is projected to increase from 30.2% in 2005 to 43.6% in 2025. The mean number of visits per rheumatologist per year is 3,758 for male rheumatologists and 2,800 for female rheumatologists. Assuming rheumatology supply and demand are in equilibrium in 2005, the demand for rheumatologists in 2025 is projected to exceed supply by 2,576 adult and 33 pediatric rheumatologists. The primary factors in the excess demand are an aging population which will increase the number of people with rheumatic disorders, growth in the Gross Domestic Product, and flat rheumatology supply due to fixed numbers entering the workforce and to retirements. The productivity of younger rheumatologists and women, who will make up a greater percentage of the future workforce, may also have important effects on supply. Unknown effects that could influence these projections include technology advances, more efficient practice methods, changes in insurance reimbursements, and shifting lifestyles. Current data suggest that the pediatric rheumatology workforce is experiencing a substantial excess of demand versus supply. Based on assessment of supply and demand under current scenarios, the demand for rheumatologists is expected to exceed supply in the coming decades. Strategies for the profession to adapt to this changing health care landscape include increasing the number of fellows each year, utilizing physician assistants and nurse practitioners in greater numbers, and improving practice efficiency.