In this study the tanning properties of glutaraldehyde were evaluated under various conditions and compared with results obtained using other aldehydes under the same conditions. Whole sheepskins (Syrian) were used in this investigation. Measuring the disappearance of glutaraldehyde from the tanning liquor provided a sound basis for evaluation of the over-all rate of tanning and fixation. Tanning was effected over a wide range of conditions. The rate of tanning and uptake of glutaraldehyde increased rapidly with increase of pH and concentration. Maximum shrink temperature also was attained rapidly and, in the higher pH ranges, was reached in about one hour. Tanning was effected with as little as 1.5per thousand (based on the drained pickled weight) of active aldehyde. Under certain conditions complete exhaustion of glutaraldehyde could be obtained from the tanning liquors. This behavior is in marked contrast to that observed in the case of formaldehyde or glyoxal. Under comparable conditions of tanning with these three aldehydes the rate of tanning increased in the order: glyoxal, formaldehyde, and glutaraldehyde.