H2+ions produced by a Philips ionization gauge (PIG) type discharge in hydrogen were injected into a cylindrical electric field which was varied in magnitude to give a maximum strength ranging from 65 to 450 kV/cm. H2+ions in highly excited vibrational states were dissociated by the electric field. The measured fraction of the H2+ions produced by the PIG discharge which were dissociated was 0.0011±0.0002 at a field of 200 kV/cm. Numerous experimental checks demonstrated that the dissociation fraction could not be attributed to effects other than electric field dissociation. The fraction is several times greater than that measured by other investigators. This difference is attributed to the method used in the preparation of the H2+ions.