This report presents a comprehensive review of efficacy studies for minimal contrasts therapy and maximal oppositions therapy. The target population was defined as children with phonological disorders who had no co-occurring impairments in hearing, receptive language, speech articulation, or oral-motor structure and function. Thirty three minimal contrasts studies from 1981 to 2008 and six maximal oppositions studies from 1990 to 2008 were identified. No studies from 2009 to 2012 were found. The majority of the studies were either Level III (descriptive studies, 34.2%) or Level IIb (quasi-experimental studies, 57.9%). Twenty three studies reported treatment duration, which ranged from six to 58 hours. Based on reports of treatment success and generalization to new linguistic and communicative contexts, it was found that minimal contrasts therapy has greater support in the literature. Additional studies using a uniform methodology will be needed to establish the validity of maximal oppositions therapy. Recommendations are made for future studies of minimal contrasts and maximal oppositions. / text