A method has been developed whereby refractive microlenses can be produced in poly (methyl methacrylate) by excimer laser irradiation at λ = 248 nm. The lenses are formed by a combined photochemical and thermal process. The lenses are formed as depressions in the substrate material (negative focal length), which makes replication necessary in order to obtain lenses with a positive focal length. The method allows for considerable flexibility with respect to the pattern of lenses and the properties of the individual lenses. In this investigation it was possible to vary the diameter of the lenses between 30 and 500 μm and the focal lengths between 300 μm and several mm.