Autohaemotherapy, after a bland treatment ex vivo of blood with ozone, is a fairly unknown medical procedure claimed to have therapeutic value in viral diseases and neoplasms. Having already shown that ozone acts as a mild inducer of cytokines, we have undertaken an investigation in normal rabbits and in normal volunteers aiming to evaluate eventual changes of some cytokine levels in plasma as well as of immunological parameters such as the Mx protein, neopterin, beta 2-microglobulin and of some acute-phase proteins after single or repeated autohaemotherapy. We have also evaluated the potential development of of side-effects. This study is the first one to show that autohaemotherapy can activate an immunological marker in normal subjects without procuring any toxic effects.