Women's treatment preferences for lupus nephritis vary widely even after adjusting for sociodemographic factors and disease severity. Attitude toward risk may partially explain interpatient variability in treatment preference. The objective of this study was to examine the association between 'risk-attitude' and patient treatment preferences in lupus nephritis. Sixty-five premenopausal women with systemic lupus erythematosus were interviewed. Patient preferences for cyclophosphamide versus azathioprine for the treatment of lupus nephritis were ascertained using an Adaptive Conjoint Analysis questionnaire. Risk-attitude was ascertained by asking patients to choose between a pair of lotteries having the same expected value but differing in spread (the difference between the worst and best outcomes). Respondents preferring the wider spread were classified as relatively more risk-seeking and those preferring the narrower spread were classified as relatively more risk-averse. Twenty-eight percent of respondents were classified as relatively more risk-seeking. Risk-seeking women were more likely to prefer cyclophosphamide for the treatment of lupus nephritis compared with risk-averse women [least square mean (+/- SD) preference for cyclophosphamide 63 +/- 3 among risk-seeking women versus 55 +/- 2 among risk-averse women (P < 0.03)]. The association between risk attitude and treatment preference persisted asthe probabilities of adverse events were varied to reflect the range of risks reported in the literature. Our results suggest that patients' relative risk-attitudes, as measured by a lottery task, are related to their treatment preferences. Differences in risk-attitude may help explain the inter-patient variability in treatment preferences.