Subject of this work is the design and the synthesis of triarylmethyl (TAM) radicals which are aimed in particular for pharmaceutical and medical applications – in vitro analysis and in vivo diagnosis. The patented syntheses of TAMs were improved and subsequently radical 13 was covalently attached to HES. Extensive investigations were carried out on solubility, stability, redox-behavior and toxicity of TAM derivatives (13, 14 and 32). The distribution coefficient was determined via EPR-spectroscopy and the dependence of the line width on the viscosity, the pH value and the oxygen content was investigated. The results show an evident dependence of the line width on the oxygen content of the surroundings and support the suitability of TAMs as oxygen-sensitive spin-probes. Subsequently, the suitability radical 14 for EPR-Imaging experiments was investigated. Radical 14 shows an evident advantage compared to nitroxide radicals, which are used to date in EPR-Imaging experiments.