In order to investigate histological results produced by laser wavelengths 514 and 585 nm (Monoline Argon Laser and cw Dye Argon Laser), tests were carried out on a haemangioma situated on the neck of a male adult. The tests were done using the hexascan, previously modified to receive two fibers, which could separately direct the wavelengths 514 and 585 nm (1 watts and 30 ms pulses), with slight pauses during the treatment of one area and another, but both areas having identical characteristics. Random histological samples were taken previous to treatment, immediately after, and a month following treatment, processing them with Mason's Trichromic. Analysis and evaluation of the samples were performed by two researchers, strange to the investigation. In addition to the typical tissue reactions to relatively long Argon pulses (longer than 100 ms), it was found that there were no significant differences in the skin and vessels histological reactions, when both wavelengths 514 and 585 nm were used.