Purpose--The aim of this paper is to describe a study of online, asynchronous dialogues between tutors and nine work-based postgraduate learners on learning through work (LtW) programmes. Design/methodology/approach-- Adopting a constructivist perspective and using a qualitative approach, 670 messages were segmented into semantic units and categorised by activity and content. Analysis borrowed from content and discourse approaches and categories were grounded in the data. Findings--Online exchanges were found to mirror those of effective face-to-face learning encounters. Learners asked questions, reported on their progress and plans, sought and gave feedback, and disclosed personal information and feelings. Tutors gave direct answers, advised and made suggestions, explained and elaborated, offered signposting and referral and provided feedback. Dialogue content was categorised as administrative/organisational, technical, affective, social, academic or relating to programme design. Research limitations/implications--Learners embarking on undergraduate level study may raise different issues from those working at postgraduate level. Practical implications--The individual categories and the framework as a whole may help new online tutors to anticipate and prepare for their role. Originality/value--The study is unusual in focusing on one-to-one online dialogues between university tutors and work-based learners. The unique contribution is a hierarchical analytical framework of dialogue topics in which "hard" and "soft" topics underpin academic dialogue. (Contains 1 table and 1 figure.)