This study sought to extract underlying beliefs towards measles, mumps and rubella (MMR) vaccination from UK parents' views towards potential motivational and organisational interventions to boost MMR vaccination. Thematic analysis of transcripts of five focus groups identified five underlying psychological themes: parents' information needs, distrust of government sources, trust of other parents, attentional biases towards risk information and problems of achieving "balance" in MMR information provision. These are likely to represent important psychological barriers to or facilitators of the effectiveness of MMR promotion interventions.