Rupture of the yolk sac was identified in leghorn chicks from six placements of a commercial hatchery that had high mortality (up to 3%) during the first 3 days. The abdomens of these chicks were filled with cloudy yellowish fluid; kidneys were swollen, and many chicks also had severe visceral urate deposition (visceral gout). No significant bacterial growth was detected. The hatchery had recently hired new sexors. After the sexors were cautioned to handle the chicks more carefully, the problem abruptly subsided. In an experimental attempt to reproduce the condition, a graded series of doses (0, 0.5, 1.0, 2.0, and 4.0 ml) of egg yolk were injected intraperitoneally into five groups of twenty 1-day-old chicks. Twelve of the 20 chicks that received the 4-ml dose died. They developed swollen, pale kidneys and had cloudy yellow fluid in the abdominal cavity, but no visceral urate deposition. Only six of the remaining 80 chicks that received lesser doses or no yolk died.