[Dalam kehidupan sehari-hari, kehidupan masyarakat sangat erat kaitannya denganperjanjian. Namun tidak banyak masyarakat yang tahu bahwa perjanjianmerupakan suatu perbuatan hukum yang memiliki konsekuensi hukum bagi parapihak yang melakukannya. Perjanjian secara hukum diatur di dalam Buku Ke IIIKitab Undang-undang Hukum Perdata pada bab berjudul ?Tentang Perikatan?.Perjanjian memiliki aspek dengan berbagai macam aspek teori yang luas didalamnya yang kemudian membentuk unusr-unsur, hingga syarat bagaimanadikatan sah. Salah satu teori ada di dalam Kitab Undang-undang Hukum Perdatadan berkembang adalah yaitu teori perjanjian diam-diam (Silent Agreement).Eksistensi dan keberadaan Silent Agreement memang ada dan diatur di dalamHukum Perdata Indonesia. Namun sayangnya hal ini tidak diatur secara eksplisitdan mendasar, hingga kerap kali penggunaannya dalam keperluan hukum,Berdasarkan permasalahan tersebut maka permasalahan yang akan diteliti olehpenulis dalam skripsi ini adalah bagaimana pengaturan secara umum tentangperjanjian secara umum di dalam Buku ke-III Kitab Undang-undang HukumPerdata, bagaimana pengaturan tentnag perjanjian diam-diam dalam Hukumperdata Indonesia, dan penerapan teori perjanjian diam-diam (Silent agreement) didalam gugatan pada putusan Mahkamah Agung Republik Indonesia No. 2178K/Pdt/2008 Dibandingkan dengan putusan Mahkamah Agung Republik IndonesiaNo. 1023 K/Pdt/2011;In daily life, the society?s life has the closest connection with agreement. Howevernot many poeple know that agreement is a legal action which has legalconsequence for the parties who do it. Agreement is legally regulated in the BookIII of Civil Code in a chapter with the title ?About Contract.? Agreement hasaspects with various aspects of the comprehensive theory in it which later formedelements, including requirement in order to be said valid. One of the available andgrowing theories in the Civil Code is the theory of Silent Agreement (PerjanjianDiam-Diam). The existence of Perjanjian Diam-Diam is existed and regulatedunder the Indonesian Civil Law. Unfortunately, this mater is not explicitly andfundamentally regulated, so that most of the time its usage in legal purpose, eitherused in an argument of lawsuit or anything else, becomes inappropriate. Based onsuch issue then the problems that will be researched by the author in thisundergraduate thesis are on how the regulation in general regulated the agreementin Book III of Civil Code, how the regulation on silent agreement is regulated byIndonesian Civil Law, and the applicability of silent agreement (Perjanjian Diam-Diam) theory in the lawsuit of the Supreme Court Decision of the Republic ofIndonesia No. 2178 K/Pdt/2008 compared with the Supreme Court Decision ofthe Republic of Indonesia No.1023 K/Pdt/2011, In daily life, the society’s life has the closest connection with agreement. Howevernot many poeple know that agreement is a legal action which has legalconsequence for the parties who do it. Agreement is legally regulated in the BookIII of Civil Code in a chapter with the title “About Contract.” Agreement hasaspects with various aspects of the comprehensive theory in it which later formedelements, including requirement in order to be said valid. One of the available andgrowing theories in the Civil Code is the theory of Silent Agreement (PerjanjianDiam-Diam). The existence of Perjanjian Diam-Diam is existed and regulatedunder the Indonesian Civil Law. Unfortunately, this mater is not explicitly andfundamentally regulated, so that most of the time its usage in legal purpose, eitherused in an argument of lawsuit or anything else, becomes inappropriate. Based onsuch issue then the problems that will be researched by the author in thisundergraduate thesis are on how the regulation in general regulated the agreementin Book III of Civil Code, how the regulation on silent agreement is regulated byIndonesian Civil Law, and the applicability of silent agreement (Perjanjian Diam-Diam) theory in the lawsuit of the Supreme Court Decision of the Republic ofIndonesia No. 2178 K/Pdt/2008 compared with the Supreme Court Decision ofthe Republic of Indonesia No.1023 K/Pdt/2011]