OBJECTIVE To evaluate the cutaneous histological and ultrastructural changes of dogs following hair removal by Alexandrite laser. METHODS Seven healthy dogs with dark hair were treated for hair removal with the Alexandrite laser and skin biopsies were taken after 0.5 h, 2, 3, 5, 10, and 30 days. Specimens were examined with light microscopy and transmission electron microscopy. RESULT Laser-treated specimens showed widespread coagulation and charring subcutaneous hair shafts. These obviously damaged follicles were randomly dispersed among intact follicles within the same treatment sites. Microscopic changes were also seen in the basal epidermis where melanin was concentrated. A low level of inflammatory response was seen up to 10 days followed laser treatment. The efficiency in higher fluence test area was better than the lower one; the degree of damaged follicles with double pulse was similar to that with single pulse. CONCLUSION Alexandrite laser irradiation results in selective damage to follicles and microscopic changes in the basal epidermis. Alexandrite laser hair removal does not lead to scar formation; the efficiency of laser hair removal is fluence-depent; the degree of damaged follicles with double pulse is not different with single one; the cooled hand piece can minimize epidermal injury.