An electrochemical method for the simultaneous determination of the diffusion coefficient and efficiency of release of probe species from thermoresponsive gels due to their volume phase transition is presented. The method combines steady-state voltammetry at microelectrodes and conductometry, and it is designed for charged, redox species. This method might be modified for uncharged systems; in this case instead of the conductometric measurement an additional independent voltammetric experiment in the solution is required. The approach presented here has been examined for positively and negatively charged and uncharged ferrocene derivatives as probes in the poly(N-isopropylacrylamide) hydrogel. The release coefficient, 0, defined as the ratio of the concentrations of the probe in the expelled solution and the swollen gel, and determined for the charged ferrocene-based probes, is greater by approximately 25% than that found for the uncharged ferrocene derivative. The larger release efficiency for the charged probes is explained in terms of substantial dehydration of polymeric chains during the gel phase transition. The experiments were performed under the conditions of excess supporting electrolyte. No influence of the identity and concentration (up to 0.05 mol/L) of supporting electrolytes (i.e., either LiClO4 or KCl) on the release coefficient was observed. The average values of release coefficients were determined to be 0.80 +/- 0.02, 1.03 +/- 0.16, and 1.07 +/- 0.14 for 1,1'-ferrocenedimethanol, sodium ferroceneacetate, and ferrocenylmethyltrimethylammonium hexafluorophosphate, respectively.