Genetic markers of lung cancer susceptibility, such as the common variant of the glutathione S-transferase Mu 1 gene (GSTM1-null), confer small probabilities of disease risk. The authors explored the influence of different approaches to communicating the small variations in risk associated with this biomarker. College smokers (N = 128) imagined that they had the GSTM1 wild-type variant versus the GSTM1 null-type variant. The authors presented lung cancer risk in 6 ways that varied the risk format (absolute risk vs. incremental risk) and the presentation style of the information (no graphics vs. graphic display of foreground only vs. graphic display of foreground + background). Presentation style had minor effects. However, absolute risk information increased negative emotions more than did incremental risk information. Perceptions of risk and negative emotions were most profoundly affected by the difference between having the GSTM1 wild-type variant versus the GSTM1 null-type variant. The authors discuss implications for conveying small probabilities related to genetic risk.