Background and aim: Clear cell sarcoma is a rare tumor with melanocytic features and is associated with tendons and aponeuroses. 18 cases were registered between 1986 and 1996 in the Scandinavian Sarcoma Group central registry. The aim was to investigate if histamine enhances the antitumor effect of dacarbazine (DTIC) and docetaxel. Methods: Human clear cell sarcoma tumor tissue was maintained by serial s.c. transplantations in nude mice. DTIC (200mg/kg, i.p.) 3 times with an interval of 2 days, docetaxel (20 mg/kg, i.p.) single dose and histamine (4 mg/kg, s.c.) daily, 5 days per week was administered in tumorbearing nude mice. DTIC and docetaxel was given separately or in combination with histamine. The tumor volumes were compared with a control group (given saline i.p.). The antitumor effect is considered signiþcant when Treatment/Control-ratio ≤ 0.4 Results: In the DTIC group the lowest TC-ratio was noted at day 21 (0.54) and in the histamine-DTIC group (0.37). Corrresponding results were 0.39 in the docetaxel-group and 0.33 in the combination docetaxel-histamine at day 13. The TC-ratio was reduced at all measuring occasions when histamine was given in adjunction with DTIC and docetaxel. Conclusions: Histamine seems to enhance the antitumor effect of dacarbazine and docetaxel in this clear cell sarcoma tumor model.