Teachers and parents are often perplexed when an intelligent student performs poorly in mathematics. Research tells us that this is often due to math disability, otherwise known as "dyscalculia". The authors define dyscalculia and describe its major subtypes. Also, the authors describe characteristics of dyscalculia and explain why dyscalculia is difficult to assess and identify. In addition, the authors explore language difficulties, math anxiety, and other factors that may cause poor mathematical performance. They also discuss quantitative and qualitative mathematical learning styles and their effects on math performance. Last, the authors explain proven successful intervention strategies that teachers can use to help students with dyscalculia to succeed in mathematics.