The effect of facial hair on the face seal of negative-pressure respirators, both half-masks and full facepieces, has been investigated. Three hundred and seventy (370) male employees were fit tested both qualitatively and quantitatively. Of these, sixty-seven (67) had fully established beards varying in length, shape, density and texture. Bearded subjects consistently failed the qualitative fit test protocol. Quantitative fit testing with half-mask respirators indicated that bearded employees had a median fit factor of 12 (8% leakage). A median fit factor of 2950 (0.03% leakage) was obtained on clean-shaven employees. An average two hundred and forty-six (246) fold drop in protection was experienced by bearded employees. With full facepiece respirators, the bearded employees had a median fit factor of 30 (3% leakage). A median fit factor of greater than 10 000 (less than 0.01% leakage) was obtained on clean-shaven employees. At least a three hundred and thirty (330) fold drop in protection was experienced by bearded employees. Results indicate that the presence of a beard greatly increases the leakage through the respirator face seal, and this leakage should not be permitted when employees are required to wear respirators.