Objective The aim of this study was to identify key domains of cultural competence from the perspective of ethnically and linguistically diverse patients. Design The study involved one-time focus groups in community settings with 61 African-Americans, 45 Latinos and 55 non-Latino Whites. Participants' mean age was 48 years, 45% were women, and 47% had less than a high school education. Participants in 19 groups were asked the meaning of 'culture' and what cultural factors influenced the quality of their medical encounters. Each text unit (TU or identifiable continuous verbal utterance) of focus group transcripts was content analysed to identify key dimensions using inductive and deductive methods. The proportion of TUs was calculated for each dimension by ethnic group. Results Definitions of culture common to all three ethnic groups included value systems (25% of TUs), customs (17%), self-identified ethnicity (15%), nationality (11%) and stereotypes (4%). Factors influencing the quality of medical encounters common to all ethnic groups included sensitivity to complementary/alternative medicine (17%), health insurance-based discrimination (12%), social class-based discrimination (9%), ethnic concordance of physician and patient (8%), and age-based discrimination (4%). Physicians' acceptance of the role of spirtuality (2%) and of family (2%), and ethnicity-based discrimination (11%) were cultural factors specific to non-Whites. Language issues (21%) and immigration status (5%) were Latino-specific factors. Conclusions Providing quality health care to ethnically diverse patients requires cultural flexibility to elicit and respond to cultural factors in medical encounters. Interventions to reduce disparities in health and health care in the USA need to address cultural factors that affect the quality of medical encounters.