A relationship was derived between the structure of halogenated heterocyclic aromatic compounds and their rate of dehalogenation in anaerobic sediment-water mixtures. Of all compounds selected, the pseudo-first order reaction rate constant was determined from the concentration-time profile, as measured with HPLC-UV. For the compounds used, half-lives for reductive dehalogenation vary from 4 up till 78 days. Subsequently, a limited number of physical-chemical parameters, expected to influence rates of transformation of the parent compounds, were selected. Finally, by using linear regression, a quantitative relationship was obtained between the Log of the measured rate constants and several of the physical-chemical parameters selected. The best relation was obtained with the parameters: molecular volume, the Log of the octanol-water-partition coefficient, and the bond strength of the carbon-halogen bond. Further research is necessary to validate and expand the applicability of the relationship obtained.<br>