Pyelonephritis was reported in horses presented for postmortem examination at Department of Veterinary Pathology, College of Veterinary Science, Hyderabad. Clinically, horses had history of colic, anorexia, apathy, stranguria and death. Pyelonephritis was diagnosed based on the necropsy lesions. Grossly, gelatinisation of fat, ballooning of intestines, haemorrhages on the base of the heart, congestion and dilated calyces of kidneys and pus in the renal pelvis were noticed. Congested liver, haemorrhagic mesentery, congestion and consolidated lungs were also noticed. Impression smears of kidneys stained by Gram’s stain and cultural examination revealed the presence of Escherichia coli, Klebsiella spp and Staphylococcus spp. Histopathological examination of kidneys revealed necrotic tubules, atrophy of glomerulus and massive infiltration of mononuclear cells (MNC).