"You Have Been Warned: the KGB and Profilaktika in Soviet Lithuania," by Mark Harrison, is No. 62 in the PERSA series. This paper provides a preliminary view of the KGB’s work to prevent the spread of subversive ideas and behaviors in Soviet Lithuania, based on the technique of “profilaktika,” or preventive warnings. The paper considers the rationale, mode of operation, scope, and effectiveness of preventive warnings. The paper is short, because it is based on a first impression of extensive documentation. The author has no intention to write a longer version. Rather, he hopes the paper may attract other scholars to work on this fascinating and important subject. The paper is available free of charge from www.warwick.ac.uk/go/persa.