The proton ligand dissociation constants of some Schiff bases of pyrazole aldehyde and the stability constants have been determined in DMF/THF-water (60:40 v/v) medium at 308.15 K. using Bjerrum-Calvin pH titration as extended by Irving and Rossotti. The stability constants are related to dissociation constants of these ligands, which depends on the substituents attached to the organic moiety.