Several approaches to couple therapy produce large and clinically significant reductions in relationship distress. However, 25 to 30 per cent of couples show no benefit from couple therapy. Adapted forms of couple therapy can effectively treat some psychological disorders and enhance adjustment to physical health problems. The specific mechanisms underlying the effects of couple therapy on relationship distress are unclear. Current attempts to enhance the efficacy of couple therapy have three foci: (1) identifying the common factors that might account for change across approaches, (2) integrating different approaches to address specific needs of particular partners and couples and (3) monitoring the progress of couples during therapy and using that information to modify couple therapy as required. Given the high prevalence of relationship distress and its association with other problems, clinicians should routinely screen for relationship distress in adults. Couple therapy needs to be considered as the focus, or part of the focus, of treatment for a wide range of adult emotional and behavioural problems.