Boutonneuse fever has become endemic in some parts of Sicily and the Italian mainland over the last five years. An account is given of the features assisting its clinical recognition and serological verification. The main nosographical aspects of the disease are described. The conditions required for certain, probable and presumed diagnosis are stated, stress being laid on the prime importance of timely clinical assessment, and the possibility of serological ascertainment when the disease is waning, or even later. Serum diagnosis via complement fixation or microagglutination will be positive in the second half of the second seven-day period of fever. It is specific with Rickettsia conorii antigens, though these have not been easy to find so far. The Weil-Felix reaction with Proteus OX19 and OX2 is significantly positive in advanced coalescence. While this is always a practical possibility, it is of indicative, and usually retrospective, value only.