Routine sun protection is recommended to prevent skin cancer. Skin cancer prevention may be particularly important for individuals at greater risk, such as those with a family history of melanoma. Our aims were to examine the prevalence of sun-protective behavior (SPB) in unaffected first-degree relatives (FDR) of individuals diagnosed with melanoma and to examine the relationship between protection motivation theory (PMT) variables (i.e., perceived risk, perceived severity, self-efficacy, response efficacy) and SPB. FDRs (n = 100), who were nominated by melanoma patients, completed a standardized, self-report questionnaire measuring demographic characteristics, melanoma risk factors, PMT variables, and SPB. The results indicated that less than one-third of FDRs used sunscreen routinely when in the sun and fewer stayed in the shade or used protective clothing on a frequent basis. FDRs with a college education and with more melanoma risk factors reported higher levels of SPB. Of the four PMT variables, greater perceived risk and greater self-efficacy were significantly correlated with higher levels of SPB. Furthermore, results of multiple regression analyses suggest that perceived risk mediated the relationship between education and SPB and between melanoma risk factors and SPB. These findings suggest that interventions to increase the frequency of SPB in at-risk individuals should highlight risk information as well as methods to improve individuals' confidence in their abilities to engage in SPB. (Cancer Epidemiol Biomarkers Prev 2006;15(1):142 -5)