While a majority of cognitive behavioural researchers and clinicians adhere to the classification system provided in the "Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)," strong objections have been voiced among behaviourists who find the dichotomous allocation of patients into psychiatric diagnoses incompatible with the philosophy of behaviourism and practice of functional analysis. The aim of this paper is to give an overview of the current debate and to analyse the tension between the "DSM-IV" and functional analysis along the following contrasts: inductive versus deductive, idiographic versus nomothetic, contextualism versus mechanism, social constructions versus real entities, and dimensions versus categories. Finally, some suggested alternatives are discussed. It is concluded that there is a need for alternative systems to the "DSM" with treatment utility.