Various general tourist markets have been successfully segmented based on the volume of tourists' expenditures in destination areas. However, the approach has been rarely employed in more narrowly defined 'special interest' tourist markets. This study tested the viability of expenditure-based segmentation in the case of a special interest market comprised of visitors to a rail-trail in the Black Hills of South Dakota, USA. Nonresident visitors were classified as light, medium, and heavy spenders based on their total expenditures in the region. Although heavy spenders comprised only 33% of the Trail's market, their spending accounted for 65% of the expenditures of the market as a whole. Compared to their counterparts, heavy spenders were more likely to have been mountain biking aficionados, to have had higher incomes, and to have had longer lengths of stay and greater involvement with recreation in the study region. Findings suggest how heavy spenders can be successfully reached, attracted, and served.