Medical students are at higher risk for depression, affecting not only their lives but also patient care. This article studied a population of medical students engaged in lecture-based learning regarding the presence of depressive symptoms and its relation to morningness-eveningness. Depressive symptoms were assessed by the Beck Depressive Inventory scale (BDI>10), and diurnal preference was assessed by the Horne & Ostberg Morningness/Eveningness Questionnaire (MEQ). Family history of depression and involvement in regular physical activity were also investigated. A total of 161 students, 77 (47.8%) males, aged 19 to 30 yrs (22.1+/-2.1) living in a city close to the equator were evaluated. Fifty-three individuals (32.9%) had depressive symptoms. Depressive individuals showed a trend to be female (p=0.07). Also, female gender showed a non-significant shift toward morningness. Fifty-eight (36.0%) subjects participated in regular physical activity. In 57 cases (35.4%), there was a history of depression in the family. Fifteen individuals (9.3%) were definitely evening type, 42 (26.1%) were moderately evening type, 44 (27.3%) were indifferent, 42 (26.1%) were moderately morning type, and 18 (11.2%) were definitely morning type. Family history of depression (OR=0.29, 95% CI=1.37-6.12) and sedentary life (OR=0.28, 95% CI=0.12-0.65) were associated with depressive symptoms. Eveningness was associated with depressive symptoms (OR=0.66, 95% CI=0.50-0.88), and this association remained significant after adjusting for the presence of familial depression and physical activity (OR=0.71, 95% CI=0.52-0.95). In conclusion, depressive symptoms are independently associated with "eveningness" in medical students. These results should be confirmed by future studies involving a larger number of subjects.