SummaryA fair correspondence was found between the label and assessed factor-VIII and -IX of the Immuno concentrates Kryobulin (factor-VIII) and Bebulin (factor-IX).The mean in vivo recovery after 42 infusions of Kryobulin in 26 haemophilia A patients was 143%; after 8 infusions of a non-lyophilized cryoprecipitate in 8 haemophilia A patients 116 %. The observed in vivo factor-VIII gain per unit of concentrated factor-VIII (Kryobulin) administered per kg body weight was 2.03. The metabolic half-disappearance time of factor-VIII when administered as Kryobulin or a lyophilized preparation prepared by the Belgian Red Cross was 8.5 and 9 hours respectively.In total 18 infusions of Bebulin have been given to 7 haemophilia B patients. Based on label activity, the mean initial dose infused was 30.71 U per kg. The mean factor-IX rise immediately after the end of perfusion was only 15.7% whereas the expected increase was 74.8%. The mean in vivo gain administered per unit of factor-IX (Bebulin) was 0.41 (0.11-0.76). The half-disappearance time of factor-IX was circa 13 hours after Bebulin and 15 hours after plasma administration.Satisfactory haemostasis was obtained with Kryobulin (42 infusions) and Bebulin (18 infusions). Out of 3 haemophiliacs treated with one of the two Immuno concentrates 3 developed overt hepatitis. As other blood products were also administered, causal relationship with the Immuno products remains uncertain. No other major side effects were noted.The advantages of the lyophilized Immuno concentrate Kryobulin over fresh or deep frozen cryoprecipitate are its pre-assayed potency, small volume, virtual absence of isoagglutinin and a reasonable solubility. The same advantages hold when Bebulin is compared to plasma.