This paper describes a simple, inexpensive multispectral imaging system for image cytometry applications. The system is based on an acousto-optical tunable filter (AOTF), a monochrome CCD camera, and a research-grade fluorescence microscope. The selected TeO2 AOTF has a 10 x 10 mm(2) entrance aperture and operates within the spectral range of 447-750 nm. The bandpass of the filter varies between 1.4 nm at 450 nm and 5.1 nm at 690 nm. The control software works within the environment of a popular image-acquisition and -processing package Image Pro-Plus, making this system easy to integrate with many existing fluorescence microscopes and cameras. Since image-cytometry applications do not require very high spatial resolution, AOTF-based systems may become an interesting alternative to more complex and expensive LCTF or pushbroom methods.