Enamel microabrasion using hydrochloric acid and pumice is an effective method to remove superficial enamel discoloration. This procedure is used in many dental offices but little is known about how different treatment combinations of hand applicator pressure on the tooth, number of applications, and duration of application affect the amount of enamel loss. This investigation studied variables of time, number of applications, and pressure individually and in combination. Twenty-seven extracted premolars were hand rubbed with an 18% HCL-pumice mixture at time intervals of 5, 10, and 20 sec and 5, 10, and 15 applications under pressures of 10, 20, and 30 g. Fifty-four longitudinal sections were cut from the treated sections and measured for enamel loss (P < 0.05). Enamel loss significantly increased as each variable separately increased. When two variables increased at the same time, a greater amount of enamel loss occurred than when one increased. The combination of 10 ten-sec applications or 15 five-sec applications with 20 g pressure resulted in enamel loss of slightly less than 250 microns.