Circadian preferences (chronotypes) as well as human sleep patterns depend on internal and environmental factors including social demands. School and work shifts are advantageous tools for studying the way social pressures impact on the biological clock. We took advantage of the Uruguayan public professional training in dance organized in two different shifts (morning, 8:30 to 12:30, and night, 20:00 to 24:00) to evaluate the influence of shifts on sleep timing and individual circadian preferences of dancing trainees (n=56) from data obtained by questionnaires (Munich Chronotype Questionnaire, MCTQ, and Morningness-Eveningness Questionnaire, MEQ) and sleep logs (SL). Although the outputs of MEQ and MCTQ significantly correlated, nocturnal dancers reported later chronotypes (measured by MCTQ) than morning dancers, but no differences in their circadian preferences measured by MEQ. Both MCTQ and SL showed that nocturnal dancers scheduled their sleep significantly later than morning ones during work and free days.