An acute respiratory distress syndrome in 10 adult dogs was usually preceded by vomiting, anorexia and lethargy followed, after a short interval, by dyspnoea. The dyspnoea became increasingly severe, despite oxygen therapy, and cyanotic respiratory failure ensued. All 10 dogs died or were killed after illnesses lasting between one and eight days. Necropsies revealed pulmonary congestion, oedema, collapse and haemorrhage with loss of alveolar epithelial cells. Early alveolar fibrosis was also found. Paraquat was identified in post mortem samples from four of the 10 dogs.