The d.c. electrical conductivity (Σ) and the relative permittivity (ɛ) were accurately measured as a function of temperature in the range 300 < T < 450 K for ammonium oxalate monohydrate (AOX), (NH4)2 C2O4H2O and potassium oxalate monohydrate (POX), K2C2O4H2O. Differential thermal analysis (DTA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) from 300 K up to 520 K were also performed for each compound. The data of the electrical parameters combined with the DTA and/or DSC thermograms suggest the existence of a possible change in the electrical conduction at 350 K for AOX and at 355 K for POX. Like most hydrogen-bonded molecules, the charge carriers may be protons and the electrical conduction is therefore protonic. At somewhat higher temperatures, dehydration and/or decomposition takes place in each compound and is reflected as a sudden loss in weight in the TGA plot.