Patent are rights given to individuals, either inventors or innovators by the state to allow them to expose their products to the public for a specific period of time (MacLeod, 2002). The exclusive right gives the patentee the right to prevent others from, selling, making, distributing, using, and the patented invention without his authority. The patent law differs from one state to another in several ways as some countries use national patent law while others use International patent law.This paper looks at the four major differences in patent laws in USA, Japan and Europe. First to file versus first to invent is a major difference that is notable in USA, Japan, and Europe. In case there are two applicants for the same patent right, the European patent Authority and Japan Patent Authority offer the right to the first applicant and not the applicant who claims to have made the invention first hence they practice first to file policy (MacLeod, 2002). In USA, whenever there are two applicants for the same patent, an investigation is done to find who the first actual inventor was by looking through the laboratory log books, date of the prototypes among other inventories. Hence, the USA practices first to invent policy. Grace period for patent application is also a major difference among these countries. Incase a product is exposed to the public either by selling the product, making advertisement or informing the investor about the product without non discloser Agreement, the patentee is given a grace period of one year to make his application for patent. The application is disqualified if it is made after a year but in Japan and Europe, the inventor is automatically disqualified for patent whenever the product reaches the public without earlier application of patent right (Susan, 2003). This forces the inventors to acquire patent rights before releasing the product to the public. The territorial area of operation in which the acquired patent is considered valid also differs in USA, Japan and Europe. Since USA is a federal government and patent law practiced is federal statute, the right granted to inventor gives him/her authority to exercise his/her right throughout the USA.He/she has powers to prevent anybody from selling, publishing or making similar products within USA. This also happens with patent rights in Japan acquired at Japan patent office which is valid throughout Japan. This is in contrast with European patent right as only twenty seven countries have signed the European patent convention treaty and the patent right acquired from the European Patent Office (EPO) in Munich can only be excised in these countries: Spain, Belgium, Romania, Cyprus, the Czech Republic, ,Estonia,, Austria, Denmark, , Finland, Hungary, France, Liechtenstein Greece, Italy, Switzerland , Germany, Luxembourg, Monaco, Bulgaria, the Netherlands, Portugal, Slovenia, Slovakia, Ireland, Sweden, Turkey and the United Kingdom (Susan, 2003). In USA and Japan, the applicant cannot acquire patent right unless he/she discloses all the details of his/her invention. The inventor presents his drawings, specifications and major steps involved when making his invention (Barton & Emanuel, 2005).This prevents the inventor from acquiring the patent before giving important details to