Our objective of this study is to develop a conceptual framework for the construct of health numeracy based on patient perceptions, using a cross-sectional, qualitative design. Interested participants (n=59) meeting eligibility criteria (age 40-74, English speaking) were assigned to one of six focus groups stratified by gender and educational level (low, medium, high). Fifty-three percent were male, and 47% were female. Sixty-one percent were white non-Hispanic, and 39% were of minority race or ethnicity. Participants were randomly selected from three primary care sites associated with an academic medical center. Focus group discussions were held in May 2004 and focused on how numbers are used in the health care setting. Data were presented from clinical trials to further explore how quantitative information is used in health communication and decision making. Focus groups were audio and videotaped; verbatim transcripts were prepared and analyzed. A framework of health numeracy was developed to reflect the themes that emerged. Three broad conceptual domains for health numeracy were identified: primary numeric skills, applied health numeracy, and interpretive health numeracy. Across domains, results suggested that numeracy contains an emotional component, with both positive and negative affect reflected in patient numeracy statements. We conclude that health numeracy is a multifaceted construct that includes applied and interpretive components and is influenced by patient affect.