Microbial tightlocks and partial tightlocks, hand-picked from a commercial field of 'Coker 315' at Florence, SC, were blended (W/W) with a Memphis territory cotton (base fiber) at the rate of 1%, 5%, and 10% tightlocks. Respirable dust generated during carding of the cotton was analyzed for endotoxin and viable gram-negative bacteria. Base fiber, 1% and 5% tightlock cottons were comparable in terms of endotoxin and gram-negative bacteria in respirable dust, despite the smaller amount of endotoxin on base fiber. Results for the 10% tightlock cotton dust were inconclusive; results for cardroom dust differed with those from remote room dust. Hand-picked white, fluffy lint from Florence contained large amounts of endotoxin which was associated with spotting at the base of the lock.