Introduction: The history of lasers in medicine. Part 1 Laser-tissue interaction: Laser characteristics; The response of tissue to laser light; Optical fibers for medical applications. Part 2 Types of laser used in medicine: Solid-state lasers for medical applications; Gas lasers for medical applications; Liquid and solid-state tunable organic dye lasers for medical applications; Semiconductor lasers for medical applications. Part 3 Lasers in diagnostics: Optical sources for optical coherence tomography (OCT); Laser spectroscopy in medical diagnostics; Optical biopsy for cancer detection; Time-resolved fluorescence polarization spectroscopy and optical imaging of smart receptor-targeted contrast agents in tissues for cancer detection. Part 4 Laser therapy and surgery: Laser therapy in ophthalmology; Lasers in dermatology; Lasers in cardiology; Lasers in urology; Lasers in gynecology; Lasers in otorhinolaryngology (ORL) and head and neck surgery; Lasers in neurology; Lasers in dentistry; Laser in orthopaedic surgery; Cancer laser therapy using gold nanoparticles; Hybrid laser technology for biomaterials; Laser safety: Regulations, standards, and guidelines for practice; Photodynamic therapy for human malignancies with superficial and interstitial illumination.