An ethnographic study was made of the portion of pre-lesson transition activity, the call to lesson time (CTL), devoted to "setting up" lessons in elementary classrooms. Participants were two teachers and 62 elementary school students in two classrooms: a grade 1-3 open classroom and a traditional third grade classroom. Videotapes of 7.5 months of classroom activities provided a record of 105 lessons. Qualitative analysis of the data used Mehan's method of analytic induction combined with Barnlund's theory of meaning. Measures coded included time spans, the cast of characters, and who said what to whom. These later data were then coded for communication content, initiator and recipient of contact, and classroom "climate." In addition, data on lessons were coded for various time and time-on-task measures, and the development of the organizational system in each class was traced. A small set of recursive rules incorporating all the data were derived, various quantitative tests were run on the data from CTLs and lessons, and a statistical description of the classroom events emerged. An experimental intervention, undertaken to enrich the data, provided additional, strikingly dramatic data about the nature of the relationship of CTL to lesson. It is concluded that the little event called CTL has more complexity and power than traditional wisdom suggests. (RH)