A review of newly developed or improved analytical techniques for characterization of insulating oils is made. The emphasis is put on recent techniques, procedures, and applications developed at IREQ in five major areas of oil characterization: thermal aging, electrical properties, particles and metals in oil, gases in oil, and low-temperature applications. It is shown that among other things, the antioxidant content, as measured by HPLC, can be a simple and reliable way to estimate oil oxidation. The influence of particles and metals in oil on a-c breakdown strength are also stressed, and an ultrasonic agitation procedure is proposed to rehomogenize oil samples before electric breakdown measurements. Finally, new trends and future developments, including static electrification and scale model studies, are pointed out.