Production of IgG antibodies is usually done in mamalian cells. Predominantly, chinese hamster ovary (CHO) cells are used for generating stably transfected cell lines and for manufacturing. In addition to large scale manufacturing, stably transfected CHO cells are also well suited for repeated laboratory scale prodution of antibodies. Once generated, such cell lines can be expanded for production according to the antibody amounts needed. In this chapter, a general introduction to CHO cell line deveopment for antibody expression and a more detailed example protocol for establishing a basic CHO cell antibody expression system are given. All high performance stable mammalian expression systems are result of intensive optimisation efforts and strongly depend on the vector, selection system, host cell line and media that are used. The basic protocol described here is based on generally available materials and should be only seen as a starting point for laboratory scale production of antibodies in CHO cells.