A series of experiments was conducted in a cubic vessel of 0.5 x 0.5 x 0.5m to investigate the effects of ignition location and vent burst pressureP(nu)on vented stoichiometric hydrogen-air deflagrations inside and outside the vessel. The results show that two overpressure peaks resulting from the vent rupture and the flame-acoustic interaction respectively, were always found for front ignition. Another overpressure peak generated by the external explosion was observed for center ignition andP(nu) < 69.8kPa. For the back ignition, three overpressure peaks successively produced by the vent rupture, the flame venting and the external explosion were recorded forP(nu) < 57.3kPa. The maximum peak overpressure inside the vessel always increases withP(nu), and the maximum peak overpressure for back ignition is significantly larger than those for front and center ignitions, and the latter two cases almost have the same values. The external overpressure-time curves present a single peak for front ignition and two peaks for back ignition. The external overpressure increases withP(nu)for front and back ignitions. However, the external overpressure increases forP(nu) < 57.3kPa, but it is insensitive toP(nu)asP(nu) > 57.3kPa for center ignition. The external flame speed increases withP(nu)for front ignition while it is independent of the latter for center and back ignitions. The maximum length of the external flame for back ignition is much larger than that for front ignition and slightly larger than that for center ignition.