A patent application is kept secret during the period between filing and publication. Thus, it is possible that two or more patent applications having the same subject matter or claiming the same invention get filed in between the period of the application date and publication date of first filed patent application.

The applicants of the later filed applications have no means to be aware of the first filed patent application at the filing stage of their applications. Nevertheless, such earlier filed patent application will have patent defeating effect and can act as an applicable prior art for the later filed applications. This type of prior art is often termed as secret prior art. Some of the other interesting names by which the secret prior art is addressed are ‘‘previously filed, subsequently published applications’’, ‘‘conflicting applications” and “non-published prior rights”.
The secret prior art (i.e. earlier filed and later published patent applications) is considered as valid prior art according to the patent laws of many countries. However, its treatment and the conditions of use varies considerably throughout the world.

This article has been aimed at understanding the concept of secret prior art, factors affecting the consideration of secret prior art, its treatment within major patenting systems (especially Europe, USA, Japan, India), effect of various patent reforms or acts on the consideration of secret prior art, and further comparing the different patenting systems with regards to the approach they follow for treatment of secret prior art.

	Europe	USA	Japan	India
Relevant Article/section	Article 54(3) EP Law	Pre AIA: 35 U.S.C. §§ 102(e)(1) and (2) Post AIA: 35 U.S.C.,§102(a)(2)	Article 29-2	S. 13(1) b of Patent act 1970
Approach	Whole content approach	Whole content approach	Whole content approach	Prior claims only
Poses bar on	Novelty only	Novelty & non-obviousness	Novelty	Novelty
Self-Collision	Self-Collision	Anti-self-collision	Anti-self-collision	Self-Collision (Prior claimed approach)
Requirements for PCT for consideration as secret prior art	European phase entry & publication in an official language of the EPO	PCT designated US published in English (Pre AIA)PCT designated US published in any Language (Post AIA)	PCT designated Japan & submission of translation	On national phase entry
Consideration of foreign priority for effective filing date	Yes	Pre AIA : No Post AIA : Yes	Yes

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