Pseudocholinesterase deficiency is an inherited or acquired condition in which the metabolism of succinylcholine, mivacurium, or ester local anesthetics is potentially impaired. In this review, genetic inheritance, variants, and testing are examined. Additionally, acquired conditions and drugs that influence enzyme activity, as well as possible treatments of the condition, are reviewed. The review of the literature was conducted by searching PubMed and Ovid Medline databases, with no limitation on date of publication. The search was limited to English-language journals only. Additional articles of relevance were obtained from reference lists of previously searched articles and via Internet searches. Numerous keywords were used in the search, and a second search was undertaken to find specific citations about acquired conditions and drugs of relevance. Nearly 250 articles were obtained and examined for importance. Fifty articles appear in the review, including case reports, research studies, and review articles.