The potential tumor seeking MRI contrast agent MnTPPS(4) was labelled with the positron emitting nuclide (51)Mn in no-carrier-added (n.c.a.) form. The complex formation kinetics were investigated and the apparent rate constants were determined under pseudo-first-order conditions. The derived bimolecular rate constants gave the Arrhenius parameters E(A)=84 kJ mol(-1) and A=2 x 10(12)s(-1)M(-1). Optimum labelling conditions were derived (radiochemical yields >99% possible, effective yields about 32%). Separation and purification of n.c.a. (51)MnTPPS(4) were performed for potential human use. All impurities were <1%.