Non-destructive detection of fatigue damage, allowing an estimate of the residual life-time of components, could contribute to a safe and reliable operation of components and installations. Ultrasonic absorption, i.e. the internal friction, of a material increases with increasing fatigue or creep damage and there are many theories trying to explain the physics behind this phenomenon. Measurement of ultrasonic absorption directly on components could provide information on the degree of damage. A laser ultrasonic method, using laser-generated pulses and optical detection, was applied to study ultrasonic absorption in fatigue specimens of different metals. A characteristic behavior of the ultrasonic absorption coefficient with increasing levels of fatigue damage was found for the titanium alloy Ti-6Al-4V. Another aim of this study was to relate the absorption mechanisms to the behavior of ultrasonic absorption observed in metals with complex microstructure. To achieve this, different ultrasonic absorption mechanisms were analyzed with respect to experimental data. A thermoelastic effect related to the size and elasticity of the microstructure is discussed as the origin of the increased ultrasonic absorption.