The efficacy of cognitive-behavioral therapy (CBT) involving exposure and ritual prevention (EX/RP) for obsessive compulsive disorder (OCD) has been well documented, as has the efficacy of pharmacotherapy using serotonin reuptake inhibitors (SRIs). Response to these monotherapies is neither universal nor complete, however, and in the past 20 years significant progress has been made in examining the efficacy of combined EX/RP plus SRI treatment. Results of randomized controlled trials that have employed adequate methodology suggest that combined treatment may afford some advantages over the monotherapies, although the effect is generally not robust and there are some negative findings. Combined treatment may be especially useful in certain clinical circumstances, however, and case examples are provided describing the use of combined treatment for one patient who presented with comorbid depression and for another who refused EX/RP because he perceived it as too threatening. Keywords: obsessive compulsive disorder; ritual prevention; pharmacotherapy Significant advances have been made in the understanding and treatment of obsessive compulsive disorder (OCD) in the past 2 decades. There is ample evidence now for the efficacy of cognitive-behavioral therapy (CBT) involving exposure and ritual prevention (EX/RP; see Franklin & Foa, 2002) and for pharmacotherapy with medications that inhibit serotonin reuptake, including the tricyclic antidepressant domipramine (CMI) and the selective serotonin reuptake inhibitors (SSRIs; see Dougherty, Rauch, & Jenike, 2002, for a review). Although the outcome data on these monotherapies support the efficacy of both approaches, they also suggest the need for the development of even more effective, better tolerated, and more durable approaches. Large studies indicate consistently that partial response to the serotonergic compounds is the norm (Pigott & Seay, 1998), side effects can limit medication dosing for at least a subset of patients, and pharmacotherapy is associated with a substantial relapse rate upon medication discontinuation (e.g., Simpson et al., 2004). CBT involving EX/RP is by no means a panacea, either: some patients refuse it because they perceive it as too difficult, some patients enter but do not complete treatment because of the anxiety associated with directly confronting feared thoughts and situations as required in EX/RP, and residual symptoms usually remain even in patients who complete intensive treatment. In light of the difficulties associated with EX/RP and SRI monotherapies, alternative approaches to OCD have been advanced. One such approach is augmentation of SRI with a second medication. Indeed, many medications have been used to augment SRI effects in OCD (Hollander et al., 2002). However, the only strategy with proven efficacy at reducing OCD symptoms in large, double-blind, placebo-controlled trials involves antipsychotic medications like haloperidol (McDougle et al., 1994), risperidone (McDougle, Epperson, Pelton, Wasylink, & Price, 2000), olazapine (Bystritsky et al., 2004; Shapira et al., 2004), or quetiapine (Denys, de Geus, van Megen, & Westenberg, 2004). However, concerns about the unfavorable side effect profile of these medications and the fact that they also appear to help some but not all OCD patients on SRIs limits the broad applicability of this approach. Other experts (e.g., Greist, 1992) have advocated combined treatment involving EX/RP and SRI pharmacotherapy. The logic of this approach is straightforward: both treatments are partially effective and have specific limitations, and combined treatment may improve efficacy by reducing the impact of these drawbacks. Below we review the empirical literature on combined SRI pharmacotherapy and EX/RP. REVIEW OF THE RANDOMIZED CONTROLLED TRIALS In order to glean information from only those studies of relevance that meet accepted methodological standards in the field (Franklin & Foa, 2002), our review was limited to studies in which: (a) patients had an established diagnosis of OCD; (b) the design included at least two treatment groups, one of which received SRI pharmacotherapy or CBT monotherapy (with or without PBO) and the other received combined treatment; (c) adequate methodology was employed, including: random assignment, sufficiently large sample sizes for statistical power, adequate treatment quality and dosage, and independent evaluation of OCD symptoms by a trained assessor. …