This paper examines the formal and functional properties of code-switching among Mexican-American children. Two formal types of code-switching, code-mixing and code-changing, are identified, and developmental patterns in their use are discussed. Two major functional types of code-switching are also differentiated. The first, situational code-switching, is discussed in terms of four parameters: participants, topic, discourse type, and setting. The second, stylistic code-switching, is subdivided for discussion into code-switching which takes place to mark: (1) emphasis, (2) focus, (3) elaboration, (4) clarification, (5) attention attraction or retention, (6) mode shift, (7) topic shift, and (8) addressee shift. The discussion of functional types of code-switching includes the presentation of a few broad developmental trends. (Author)