For various acids and bases dissociation constants were determined conductimetrically in m-cresol. A glass electrode was calibrated by means of some compounds with dissociation constants known from conductivity measurements. Potentiometric titrations with this calibrated glass electrode gave dissociation constants of some other acids and bases in m-cresol. The value 2·10−19 was found for the self-dissociation constant of m-cresol. From the difference pKa (cresol) - pKa (pyridine) for those compounds having acid or base strengths which are not levelled either in pyridine or m-cresol, it was found that the solvent m-cresol has a basicity about 8 pK units less than that of pyridine.