This study of code switching among Puerto Rican children attending a New York City public school focuses primarily upon the correlation between interaction rules, as perceived by the participants, and code switching. Code switching strategies of a seven-year-old boy, an eight-year-old girl, and a 10-year-old girl in the bilingual third grade class were analyzed in two interactions: an individual interview with the researcher, a female New York Puerto Rican, and a domino game in which all three children participated. The interviews were conducted in both Spanish and English; the interviewer began in Spanish and then switched to English without warning. The study reaffirms other research concerning the ability of children to switch situationally with ease, the superior power/status of English vs. Spanish, and the use of stylistic or conversational code switching for emphasis, addressee specification, elaboration, and idiomatic expressions. The analysis also suggests that, as expected, bilinguals beyond the six-year-old "pre-operational stage" do not "only focus on one feature or variable of a situation at a time" (Genishi, 1976), but their language choices often reflect awareness of several social, linguistic, and situational variables. Child-adult dyads in question-answer interactions constrain code switching, and informal peer interactions stimulate it. Implications for bilingual education and appropriate research methodologies are briefly considered. Examples of dialogues are included. (SW)