The critical current density Jc was determined magnetically in polycrystalline sintered specimens of YBa2Cu3O7-δ as a function of magnetic field and temperature for 0.02≤δ≤0.31. The critical temperature of these quenched specimens decreases almost linearly with increasing δ. The highest Jc values at all temperatures and fields are found in the specimen with δ≈0. However, when taking into account that the thermodynamic critical field Hc decreases quite strongly with increasing δ it is concluded that the density of pinning centers increases as the oxygen deficiency increases. Low temperature equilibrations (keeping constant stoichiometry) significantly affect Jc values. © 1991.