A fungal disease of Platanus spp. is reported from Central Chile. The fungus was observed as greyish-white spots mostly in February and March 1987, mainly on young leaves and vigorous shoots, causing their deformation and reducing their growth. No teleomorph was observed. Disease susceptibility apparently varies by host species, vigour and length of growth period. Comparison with published descriptions enabled the fungus to be identified as the Oidium state of Microsphaera platani Howe. Control of the disease is discussed.