Many popular medicinal plants have been used indiscriminately without a solid scientific basis for their efficacy, as is the case of Solidago microglossa DC, popularly known as arnica-do-Brasil or simply arnica. This plant is used to treat inflammation and to accelerate the healing of wounds. In this work we examined the effect of daily intraperitoneal applications of a crude aqueous extract of arnica on the cicatrization of open cutaneous wounds in Wistar rats. Male Wistar rats were randomly allocated to a control group that received no drug, a sham group that received only the drug vehicle, and a treated group that received daily intraperitoneal injections of a saline solution of arnica (16.1 mg.kg^-1), for 7 or 14 days after excision of a dorsal cutaneous flap. The area of the lesion and the amount of collagen fibers in the wound were monitored. By the 7th day of observation, there were no significant changes in the area of the lesions or in the amount of collagen fibers in the wound. However, by the 14th day of treatment, there was a small but significant reduction in the area of the wound with no significant change in the amount of collagen fiber deposition. The lack of significant changes in the serum levels of alanine aminotransferase and aspartate aminotransferase indicated that Solidago microglossa DC was not hepatotoxic at the dose used. But the LD₅₀ and LD₁₀₀ for arnica in rats were 54.7 and 86.2 mg.kg^-1, respectively, which were just 3.4 and 5.4 times higher than that therapeutic dose (16.1 mg.kg^-1), what means that the crude aqueous extract of arnica cannot be used systemically with enough safety to avoid intoxication. The wound-healing effect of arnica must be object of further investigation using the isolated constituents of the crude extract.