The aim of this paper is to highlight key advances in the cognitive-behavioural treatment of obsessive compulsive disorder over the course of Professor Lars Goran Öst’s illustrious career. The paper will focus on three specific areas of interest: the treatment of obsessions, compulsive checking and the fear of contamination. It will also highlight recent advances concerning the broader need to ensure that treatment is acceptable. An increase in acceptability could result in improvements in completion rates so that more patients benefit from the recent improvements in the science and therapy for this disabling disorder.