The Perkin-Elmer DSC-lB differential scanning calorimeter is now a relatively standard laboratory instrument. Although reasonably well designed, it is possible to improve the operation significantly with a few simple modifications. The most major of these is thermostating the cell compartment. Using a dry nitrogen atmosphere outside as well as inside the thermostated cell greatly reduces noise and decreases drift. Sub-ambient operation under these conditions becomes relatively simple. The baseline drift becomes very reproducible-a significant aid in heat capacity measurement. Simple electronic modifications in the control potentiometers also bring about significant improvements. Directions with drawings and sample runs contrasting operation are given for the optimization of this instrument. © 1974.