The concentrations of immunoglobulins A (IgA) and serum albumin (SA) determined in sputum by electro-immunoassay have been compared after the extraction of proteins by two methods: 1) ion exchange chromatography and 2) mechanical agitation at high ionic strength. No significant difference of IgA is observed between the two methods. On the contrary, a very significant decrease in the concentration of SA is observed by the chromatographic extraction which is incomplete when pH - value of extract is lower than that of the isoelectric point of SA.