Pennsylvania also requires a permit to carry in a vehicle, whether openly or concealed. However, for the purposes of carrying in a vehicle only, Pennsylvania recognizes permits from any state. However, you cannot carry a concealed firearm on your person outside a vehicle in Pennsylvania except with a Pennsylvania permit or a permit from one of Pennsylvania's reciprocal states.
See http://www.attorneygeneral.gov/crime.aspx?id=184for Pennsylvania's current reciprocity list.
18 Pa.C.S.A. § 6106. (effective May 9, 2006)
(a) Offense defined.--
(1) Except as provided in paragraph (2), any person who carries a firearm in any vehicle or any person who carries a firearm concealed on or about his person, except in his place of abode or fixed place of business, without a valid and lawfully issued license under this chapter commits a felony of the third degree.
(2) A person who is otherwise eligible to possess a valid license under this chapter but carries a firearm in any vehicle or any person who carries a firearm concealed on or about his person, except in his place of abode or fixed place of business, without a valid and lawfully issued license and has not committed any other criminal violation commits a misdemeanor of the first degree.
(b) Exceptions.--The provisions of subsection (a) shall not apply to:
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(11) Any person while carrying a firearm in any vehicle, which person possesses a valid and lawfully issued license for that firearm which has been issued under the laws of the United States or any other state.
(12) A person who has a lawfully issued license to carry a firearm pursuant to section 6109 (relating to licenses) and that said license expired within six months prior to the date of arrest and that the individual is otherwise eligible for renewal of the license.
(13) Any person who is otherwise eligible to possess a firearm under this chapter and who is operating a motor vehicle which is registered in the person's name or the name of a spouse or parent and which contains a firearm for which a valid license has been issued pursuant to section 6109 to the spouse or parent owning the firearm.
(14) A person lawfully engaged in the interstate transportation of a firearm as defined under 18 U.S.C § 921(a)(3) (relating to definitions) in compliance with 18 U.S.C. § 926A (relating to interstate transportation of firearms).
(15) Any person who possesses a valid and lawfully issued license or permit to carry a firearm which has been issued under the laws of another state, regardless of whether a reciprocity agreement exists between the Commonwealth and the state under section 6109(k), provided:
(i) The state provides a reciprocal privilege for individuals licensed to carry firearms under section 6109.
(ii) The Attorney General has determined that the firearm laws of the state are similar to the firearm laws of this Commonwealth.
Please note that section 6106(b)(15) has not yet been used to grant reciprocity to any state that recognizes Pennsylvania permits but which has not signed a formal reciprocity agreement with Pennsylvania.