The paper deals with the problem of carrying on online written exams in the University of Milan, suddenly closed due to the Covid-19 emergency. Main goal of the paper is to present and compare the different scenarios envisioned, depending on the number of students to be monitored in parallel to avoid cheating. For limited numbers, direct monitoring by the teacher has been suggested, with different supports depending on the type of exam proposed by the teacher (open vs. closed answer questions, presence of handwritten parts). For larger numbers, a proctoring system has been adopted, after some comparisons between two commercial solutions. Results show a very large adoption of a solution allowing teachers to monitor in real time students answering open questions on their home computers. [For the full proceedings, see ED621620.]