Thus, the aims of this study are: (1) To demonstrate, using a MTS colorimetric method to evaluate cell viability, the antitumor action of the NK-1 receptor antagonist L-732,138 against human melanoma COLO 858, MEL HO, and COLO 679 cell lines, and to show that this antitumor action occurs through the NK-1 receptor; and (2) To investigate whether the NK-1 receptor antagonist L-732,138 produces apoptosis in the three melanoma cell lines studied. This evidence concerns the gene TACR1 and melanoma.