In this paper we present several measures taken in Lisbon to prevent contagion by the plague, from the ships that arrived at its port. Some of the legislation that was enacted from the 15th century onwards will be analysed, especially to control, from the health point of view, the arriving travellers and to ensure the isolation of those who were a potential threat. Special attention will be paid to two regiments written at the end of the Sixties, regulating, in a detailed way, how to carry out such control.