This study evaluated labelling efficiency and radiochemical purity of (99m)Tc colloid albumin to identify an optimal labelling protocol for sentinel node detection. Results indicate that a 72 h eluate is not recommended for high specific labelling of (99m)Tc colloid albumin. Ex vivo, significantly higher count rates were reached using a 2h eluate in vacuum or nitrogen. Labelling 26 MBq/microg (99m)Tc colloid albumin with a 2 h eluate under nitrogen is recommended because of the ease of labelling.