© 2015 Watkins et al. Background: Prenatal alcohol exposure is an important modifiable cause of adverse fetal outcomes during and following pregnancy. Midwives are key providers of antenatal care, and it is important to understand the factors which influence their ability to provide appropriate advice and support to women about alcohol use in pregnancy. The main aim of this study was to develop a psychometrically valid scale to evaluate midwives' beliefs about assessing alcohol use during pregnancy. Method: A self-administered questionnaire was developed to evaluate midwives' beliefs about assessing alcohol use during pregnancy, including beliefs about positive and negative consequences of asking about alcohol use, and beliefs about capacity to assess alcohol use. The questionnaire was sent to 245 midwives working for a state-wide country health service in Western Australia. Exploratory factor analysis was used to identify the latent constructs assessed by the 36 belief items and provide initial construct validation of the Asking About Alcohol (AAA) Scale. Results: Of the 166 (67.8 %) midwives who responded to the survey, 160 (96.4 %) completed one or more of the belief items and were included in this analysis. Factor analysis identified six subscales which assessed beliefs about discomfort, capacity, effectiveness, role, trust and knowledge. Midwives held the most positive beliefs about their capacity to ask and the effectiveness of asking about alcohol use, and the least positive beliefs about women's knowledge about alcohol use and discomfort associated with asking about alcohol use in pregnancy. Midwives' beliefs about their role and the effectiveness of asking were most strongly associated with the intention to ask all pregnant women about alcohol use during pregnancy (r = -0.59, p <0.001 and r = -0.52, p <0.001). Conclusions: Our analysis has identified key constructs underlying midwives' beliefs about the assessment of alcohol use during pregnancy. The AAA Scale provides a basis for improved clarity and consistency in the conceptualisation and measurement of midwives' beliefs which can be used to enhance our understanding of factors influencing midwives' ability to deliver interventions to prevent alcohol use during pregnancy. The constructs identified in this exploratory analysis require confirmatory analysis to support their validity and generalizability.