PURPOSE: We noted that in a catheter, glue-lipiodol mixtures (GLM) prematurely turned into a cast duringembolization of brain arteriovenous maliformation, and to avoid this problem, added tungsten to GLM. The reactiontime and hardness of GLM were then evaluated in vitro. MATERIALS AND METHODS: Six lots of Lipiodol (Nos.97LU009A, 96LU018A, 96LU017A, 96LUollA and 95Lu020A)(Laboratoire Guerbet, Cedex, France) and three lots HistoacrylBlue (2/7121, Ex. Date 03/99 (993);2/6263, 06/98 (986);2/6132 03/98 (983))(B. Brown, Melsungen, Germany) weremixed in a 5cc bottle at concentrations of 25-50%(glue:lipiodol=1:1 to 1:3) and observed for two weeks. Thehardness of polymerized GLM was classified as liquid, gel, semi-solid or solid. After the addition of tungsten ortantalum powder (0.2gm) and a drop of blood to GLM, different series of experiments were performed. pH wasmeasured in distilled water mixed with tungsten of tantalum(0.1 to 0.5 gm). RESULTS: At a concentration of 50%,most GLM turned into solid casts within 48 hours;at one of 25%, most GLM gelled within 24hrs. At concentrations of28 and 33%, hardness was between that of a solid and that of a gel. After the addition of tungsten to 50% and 25%GLM, this remained in a liquid state until two weeks later, regardless of lipiodol products. In 5cc distilledwater with 0.1 to 0.5 gm tungsten, pH changed from 3.5 to 2.6, and on the addition of tantalum from 6.4 to 5.7.The addition of blood to the mixture immediately turned the cast solid at a GLM concentration of 50%, andsemi-solid at one of 25%. CONCLUSION: The reaction time of GLM differed according to the lot number of lipiodol.The addition of tungsten seemed to prevent premature cast formation by decreasing pH;the mechanism was similar tothat observed when acetic acid was added.