P.H.A. and Concanavalin A stimulated lymphocytes culture supernatants were comparatively studied in 23 volontary normals and in 46 patients with nephrotic syndrome. Intradermal injections to guinea-pig demonstrated a permeability increasing and pro-inflammatory factor. Vascular permeability (immediate reaction) is determinated by blue Evans technique. Delayed reaction is assesed by the cutaneous inflammatory process (erythema, induration); pathologically it is defined as polymorphonuclear and mononuclear infiltration. Differences are highly significant between nephrotic patients and normal subjects. This biological activity is not observed with control supernatants (medium plus normal human serum and P.H.A. or Conca A). Positive results were also found with M.E.M. eagle culture supernatants of nephrotic stimulated lymphocytes. To date lymphokines have been studied especially in animals. In human, they have been found only after concentration. Variations in lymphokine production may be present in some pathologic states.