This manual covers the Ducati Monster 620 and Monster 400 models, produced from 2004 onwards. These motorcycles are renowned for their minimalist design, characterized by an air-cooled, Desmodromic V-twin engine and a distinctive trellis frame. Offering a middleweight naked sportbike experience, the Monster series is celebrated for its iconic styling and rider-focused engineering. The 620 variant typically features electronic fuel injection and produces approximately 63 horsepower, while the 400 model, often carbureted, delivers around 45 horsepower. These Italian-designed machines are intended for enthusiast riders seeking a motorcycle with strong character and engaging performance. This comprehensive digital workshop repair manual, presented in English and totaling over 500 pages, is designed to assist owners, technicians, and mechanics in maintaining and repairing their Ducati Monster 620 or 400. It provides detailed instructions for all major systems, including engine mechanicals, fuel and ignition systems, electrical components, transmission, brakes, suspension, cooling, chassis, and bodywork. The manual covers routine maintenance, troubleshooting, diagnostic procedures, and complete component overhauls, along with specifications for special tools. Its extensive coverage ensures that users can perform everything from simple oil changes and valve adjustments to complex engine rebuilds.