This study was an initial attempt to operationalise Moore's transactional distance theory by developing and validating an instrument measuring the related constructs: dialogue, structure, learner autonomy and transactional distance. Data were collected from 227 online students and analysed through an exploratory factor analysis. Results suggest that the instrument, in general, shows promise as a valid and reliable measure of the constructs related to transactional distance theory. Potential refinement of the instrument and future research directions are included at the end of the article.