COVID-19 pandemic led many countries to implement lockdown measures. Italy declared lockdown from 9th March to 3rd May 2020, and universities shifted to online classes. Home confinement could prevent students from achieving the physical activity and sleep levels recommended for their psychophysical health, and medicine students are already known to be at risk of inactivity and reduced sleep due to their time-consuming curricula. This study aimed at describing medicine students' behaviours during lockdown and comparing them with pre-lockdown data and current recommendations. A crosssectional questionnaire survey was conducted among 6th-year Italian medicine students (n = 714; age=25 ± 2 y; female: 62%; male: 38%) in October-November 2019. The same survey was repeated in 6th-year students during lockdown (n = 394; age=25 ± 2 y; female: 73%; male: 27%), and extended to 1st-5th year (total 1st-6th-year sample during lockdown: n = 1471; age=23 ± 2 y; female: 70%; male: 30%). International Physical Activity Questionnaire Short Form (IPAQ) and selected questions from Pittsburgh Sleep Quality Index were administered to evaluate physical activity, sitting and sleep time. Decreased physical activity, and increased sitting and sleep time were observed from pre-to during lockdown in 6thyear students (p<0.01). 1st-6th-year students featured 10 [8-12] hours sitting (median [Q1-Q3]) and an IPAQ score of 1170 MET-min/week. Even participants with higher physical activity featured high sitting time. Sleeping less than recommended (<7 h/night) was associated with more sitting time and less energies to perform daily activities. Strategies fostering compliance with current guidelines for physical activity, sedentary behaviour and sleep should be implemented, especially in case of a repeated or intermittent lockdown.