One hundred seventy single-rooted teeth were tested in vitro to evaluate the apical seal produced by the McSpadden Compactor and lateral condensation with a chloroform-softened primary cone. The obturated teeth were centrifuged in India ink, decalcified, and cleared. The degree of ink penetration into the canal provided a measure of the apical seal. Teeth filled with gutta-percha and Grossman's sealer using the McSpadden Compactor had statistically less apical leakage than teeth filled with a chloroform-softened primary cone and sealer using lateral condensation (p<0.005). Problems encountered in using the McSpadden Compactor include: (a) vertical root fractures, (b) cutting of dentin, and (c) breakage of compactors.