Abstract UAl3-Al and UAl2-Al fuel plates (50 wt% UAl3 or 45.5 and 54.5 wt% UAl2, respectively, 220 mm × 40 mm × 1.3 mm ) were irradiated in a pressurized water loop of the FR 2 (Karlsruhe). The maximum heat flux through the plate surface was about 100 W/cm2, the surface temperatures between 70 and 185°C. The uranium burnups were 5 3 to 72% in the main series. The fuel swelling, the overheating behaviour and the irradiation-induced reaction of the fuel particles with the Al matrix were studied, the latter by quantitative image analysis, microprobe and microhardness measurements. The results show that Al-base dispersion fuels containing UAl3 or UAl2 are likewise suited for high burnups in research reactors. A uranium burnup of 40% is permissible in any case up to 180°C. For higher burnups up to 60%, UAl2-Al fuel seems suitable without reservation, whereas in UAl2-Al fuel plates there is a risk of heavy blister formation on overheating above 400°C. Above a burnup of 30 to 40%, fission product precipitation processes will strongly influence the behaviour. Below that limit the swelling observed was considerably lower than the value of about 6 vol%/1021 f/cm3 given in the literature. The reaction of UAl3 and UAl2 fuel particles with the Al matrix to U1−xAl4 does not increase the volume percentage of the particles at high burnup, which took up to about 60 vol% for 55 wt% UAl2.