The quality of a number of commercial human albumin kits used at Danish hospitals for preparation of 99mTc-labelled human serum albumin has been investigated by column chromatography and HPLC. In general, the radiochemical purity was found to be low (75% or less). In some cases with a poor radiochemical purity, the main radiochemical impurity, 99mTc-labelled tin colloid, amounted to 29% or more. A large molar tin to albumin ratio seems to lead to a low radiochemical purity and it is suggested that products with a high content of stannous chloride may be more correctly termed 99mTc-albumin/tin-colloid kits.