Abstract: Research in dyslexia over the past 30 years has vacillated between a single factor and multiple factors for reading deficits with findings of support for both views. This review covered 30 years of research with the aim of determining if a single factor such as phonological processing explained the majority of dyslexic deficits or if multiple factors described as subtypes were required. Major components of phonological processing were found to be phonological awareness and phonemic representation. Major subtypes besides phonological processing were found to be visual processing and naming speed with some evidence of auditory processing deficits. A variety of remediation and intervention techniques and programs were suggested. A number of theories such as connectionist and dual deficits were developed to explain various deficits. Correlational research in other areas such as genetics and neurology were also explored. Critiques involved definitions, measurements, analysis, and participants. The conclusions from the review are that while some sort of phonological processing deficit is involved in the majority of dyslexic cases, visual and naming speed subtypes are also involved in a substantial number of cases.