Infectious tenosynovitis was diagnosed in three separate outbreaks in a commercial White Leghorn hens, though not previously reported in adult White Leghorns (3). Clinically affected flocks had decreased production and increased daily mortality, with many hens showing signs of the so called "cage-fatigue bluecomb" syndrome. Most sick birds had lesions typical of infectious tenosynovitis, with pronounced cyanosis and dehydration. Dead birds had signs of acute septicemia. The course of the disease (about 8 weeks) was not altered by the medicinal regimens tried. Young laying-age flocks were most seriously affected. Production losses averaged 15 to 20%, and mortality reached 5% per month during the recovery phase.