Cryoglobulins are immunoglobulins or immune complexes which precipitate at a temperature lower than 37 degrees C and re-dissolve when rewarmed. So their collection and processing are critical. We describe the methodology used in the biochemical laboratory of Military hospital Laveran (Marseille) for detection determination of type and quantitation of cryoglobulins. In this study, we have found cryoglobulins in 53% of healthy subjects and in 77% of patients with chronic hepatitis C.