A master service agreement is a contract reached between parties, in which the parties agree to most of the terms that will govern future transactions or future agreements. A master agreement permits the parties to quickly negotiate future transactions or agreements, because they can rely on the terms of the master agreement, so that the same terms need not be repetitively negotiated, and to negotiate only the deal-specific terms.
Contracts in the information technology, contract research, and similar "open ended" fields are often negotiated as a "Master Service Agreement" and a "Statement of Work". Typically, the Master Service Agreement specifies generic terms such as payment terms, product warranties, intellectual property ownership, dispute resolution, and the like. Each project - a program to be written, a research project to investigate murine effects of a compound, or the like - is negotiated in a Statement of Work, a project-specific rider to the Master Service Agreement, to specify the problem to be solved, schedule, price, and the like.