This document outlines the classification rules for medical devices as defined by the European Medical Device Directive (MDD 93/42/EEC). It discusses four general classifications for medical devices - non-invasive, invasive, active, and special rules - and provides more details on the classification of Class 1 medical devices. Class 1 medical devices are the lowest risk devices, including those that only touch intact skin, store substances for administration, act as a mechanical barrier, are used orally or in body cavities for short periods, or are reusable surgical instruments used transiently.