With the cooperation of several commercial mills, microbiological studies were carried out in the carding area under various conditions. This paper presents summary data on the dust levels as recorded by VE or PCAM recorders and the endotoxin level as measured by the Limulus amebocyte lysate test. The constancy of the mill airborne endotoxin and dust are emphasized over both short term and long term studies. A few mills processing polyester are included for comparison.