PURPOSE To investigate the general toxicology of mangafodipir trisodium (MnDPDP, Teslascan). MATERIAL AND METHODS Studies were performed in accordance with standard methods and in compliance with regulations current at the time of conduct. RESULTS Single-dose studies in rodents and dogs showed that MnDPDP was tolerated at doses of approximately 2000 mumol/kg, approximately 400 times a single imaging dose of 5 mumol/kg. The single dose tolerance of MnDPDP was approximately 10 times greater than MnCl2. A good safety profile of MnDPDP was also shown in repeat-dose studies (3 weeks), in which the no-observed-adverse-effect level for the rat, monkey and dog was 116, 29 and 10 mumol/kg, respectively. The local tolerance studies indicated that no adverse local tissue reactions are likely to occur after i.v. injection. Other studies indicate that accidental spillage of MnDPDP onto the skin is not expected to lead to significant systemic exposure, or to local irritation or hypersensitivity. MnDPDP was not genotoxic in a battery of several different tests. CONCLUSION MnDPDP was shown to have a good safety profile suitable as an hepatobiliary MR contrast agent for i.v. administration.