A novel pyroelectric thin film sensor with a subnanosecond response time is described. The use of this device as detector for radiation-induced thermal wave phenomena is then discussed and this detection scheme compared with more established photoacoustic and photothermal techniques. This detector provides at negligible cost a unique combination of extreme time resolution with utmost sensitivity. This sensor is compatible with most media: ultrahigh vacuum, air, most liquids and a large variety of excitation sources can be utilized together with this detector. Photons throughout the entire spectral range from radio waves to X-rays, electrons, ions and neutral particles have been used to probe the sample property of interest. When using a pulsed laser for excitation of a sample that is directly deposited onto the pyroelectric element the spectral resolution and temporal and spatial definition of the pulsed laser can be combined with the high sensitivity and large bandwidth of the pyroelectric sensor. This unique combination of advantageous features makes this technique the method of choice for most applications in the area of thin films. Examples emphasizing the versatility and the unique properties of this new detection scheme as well as its inherent limitations are discussed. Typical applications in the thermal analysis and spectroscopy of thin films are reviewed. © 1990.