The variety of microbiological tests makes it difficult, if not impossible, to prescribe a single, comprehensive method for validating all types of tests. By their very nature, microbiological tests possess properties that make them different from chemical tests. Consequently, the well-known procedures for validating chemical tests are not appropriate for many microbiological tests. Yet, it is necessary to validate microbiological tests if they are to be useful for controlling the quality of drug products and devices. Test-method validation provides assurance that a method is suitable for its intended use. Given this definition, any rational company would want to be sure that its methods are validated.