N-Ac-4-S-CAP is a compound that exhibits selective cytotoxicity towards melanin-producing cells in mouse hair follicles, causing 98% depigmentation. Within four hours of intraperitoneal injection, visible changes occur in these melanocytes, including the aggregation of melanin granules and nuclear condensation. Electron microscopy reveals progressive destruction of these cells, evidenced by swelling of membranous organelles, nuclear condensation, and cytoplasmic vacuolization, leading ultimately to complete cell death. N-Ac-4-S-CAP selectively targets active melanin-producing melanocytes but does not appear to affect precursor or dormant melanocytes. These properties suggest potential applications for N-Ac-4-S-CAP in melanoma suppression or skin whitening.