Background: Allergic reactions to metals and metal salts used in tattoo pigments occur surprisingly frequently. For this reason, this study focused on the determination of thallium (Tl) in the samples of color tattoo inks. These inks are commonly used in tattooing processes worldwide. Material and Methods: The samples were analyzed with the use of differential pulse anodic stripping voltammetry. The stripping anodic peak current of Tl was linear over its concentration range of 0.5–6.0 μg/l, which corresponds to 2.45×10^–9–2.94×10^–8 M. The determined value of the limit of detection (LOD) was equal to 0.149 μg/l (7.29×10^–10 M). Results: The obtained results revealed a wide range of Tl contents in tattoo inks, i.e., 0.0029–0.4275 μg/g. The content of this metal varied substantially depending on the pigment used in tattoo inks. Conclusions: Thallium was identified and determined in all tested samples. Its content depends on the country of origin but it does not depend directly on the color. The lowest content of Tl was found in the pink ink and the highest in the violet ink (from Israel), and a similar content was also found in the yellow ink (from Israel). The use of colored inks in larger quantities (a dense pattern and a larger surface area covered) may potentially pose a health risk. The danger of Tl poisoning from tattooing depends on the type of the ink (color) and its origin. As Tl is not considered a micronutrient, introducing such a Tl content into the body may be associated with a potentially harmful accumulation of this metal in body organs, causing various types of ailments and toxic effects primarily on the nervous, skeletal and circulatory systems. The obtained results suggest that tattooists may be exposed to the toxic effects of Tl in tattoo inks. The analytical data presented in the paper may constitute the basis for determining the acceptable limits of toxic Tl contents in tattoo inks. Med Pr. 2020;71(4):405–11