If you were convicted of a misdemanor, you may be elgible for an expungement. If you were convicted of a misdemanor and are still on probation, you may request an early release from probation and then file a petition for expungement. If you successfully completed probation, you may simply file a petition for expungement. If you served time in a state prison, you are probably not elgible for an expungement.
Take a free eligibility test at RecorGone.com
Some convictions are not elgible for en expungement. If you were convicted of any of the following offenses, you are not eligible for a dismissal: Vehicle Code Section 42001(b) which includes sections 2800, 2801 and 2803; Penal Code Section 261.5(d), 286(c), 288, 288a(c), 288.5 and 289(j).
For a better idea on whether you are elgible for expungment, take a look at Recordgone's online tool that walks you through the process. It will give you a good idea of whether are likely to succeed in a request for expungement from a misdemeanor.