Observations on the development of the horse chestnut leafminer on red horse chestnut ( Aesculus x carnea H.) were carried out in Wrocław, Lower Silesia, Poland, in 2001–2003. Three generations of the pest were recorded to lay eggs on the red horse chestnut leaves. Although females of each generation deposited eggs abundantly, the hatching larvae died after a short period of feeding in the plant’s leaves and the species did not complete its development on this tree. Mostly L 1 and L 2 larvae were found inside the leaf mines. The observed leaf damage was, therefore, negligible