The ISO 'Guide to the Expression of Uncertainty in Measurement' (GUM, 1993) establishes a unified method for evaluating and stating measurement uncertainties, that has been accepted by nearly all calibration services and most test cooperations in all parts of the world. In vibration measurements and calibrations using laser interferometry, the application of the GUM may be difficult and very time- consuming unless some possibilities of simplification are made use of. After a brief introduction to the basic procedure specified in the GUM for the calculation of the measurement uncertainty, a survey is given of the problems typically encountered in uncertainty calculations when vibrations are measured or accelerometers calibrated by laser interferometry. It is shown how a model function of simple structure can be established for the usually complex relationship between the output quantity (e.g. sensitivity of an accelerometer), the quantity to be measured (e.g. acceleration) and various influence quantities (noise, transverse motion, base strain etc.). Among other things, non-linear effects such as the influences of distortion, hum and noise can be properly taken into account. The uncertainty evaluation is demonstrated and explained by the example of the measurement of the displacement amplitude of a sinusoidal vibration using Michelson interferometry and by the example of the primary vibration calibration of an accelerometer.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.