The agreement also contains provisions for undisclosed test data and other data that are required for governments to authorize the marketing of pharmaceutical or agricultural chemicals using new chemical units. In such a situation, the government concerned must protect data from unfair commercial uses. In addition, members must protect this data from disclosure, unless it is necessary to protect the public or no action is taken to ensure that the data is protected from unfair commercial use. The TRIPS agreement provides for transitional periods that give developing countries additional time to bring national laws and practices into line with TRIPS rules. There are three main transit periods. The first was the 1995-2000 transition period, at which time countries were required to implement the TRIPS agreement. The 2000-2005 transition period allowed some countries to delay the protection of patents produced in areas where protection was not as well protected at the time the TRIPS agreement came into force in that country. These countries were allowed to follow a five-year patent regime for technologies and products they had not yet granted for patent protection, such as pharmaceuticals and agrochemicals. During the transitional period, these countries are required to accept patent applications from 1995 and to keep these applications open in a mailbox until the mailbox opens in 2005, when applications are reviewed. The third transition period will allow least developed countries (LDCs) until 2006 to meet their obligations under the TRIPS agreement, given their economic, financial and administrative constraints. This period may still be extended by the TRIPS Council at the request of a member of the LDC.

LDCs now have a further extension until 2016 for patents on medicines and exclusive marketing rights through the Doha Declaration on the TRIPS and Public Health Agreement. As a result, LDCs do not need to plan and enforce patents and data protection for drugs by January 1, 2016 (see below). Transitional periods have resulted in patented drugs or drugs prior to the implementation of their TRIPS obligations not receiving patent protection, allowing for general competition. Patented drugs after the implementation of their TRIPS commitments in developing countries are gradually entering the market and will account for an increasing share of commercialized drugs. After 2005, when all developing countries are required to grant patent protection for pharmaceuticals and mailbox patents are processed, significant change is expected.