A pulmonary surfactant reduces surface tension at the air/liquid interface of the alveoli and stabilizes alveoli at low lung volumes. Surfactant deficiency and dysfunction were shown to be present in a number of pulmonary diseases, and surfactant replacement therapy is the common clinical conduct. The hydrophilic SP‐A (surfactant protein A) is absent when solvent extraction was used during exogenous surfactant production. Addition of SP‐A to the surfactant preparation increases the surface activity and completely counteracts inhibition by blood proteins. SP‐A recognizes and binds to carbohydrate structures on the surfaces of pathogenic micro‐organisms, and acts as opsonins or cross‐linking molecules by binding to a variety of cells that participate in the pulmonary immune response. The purification procedure yielded 206 mg of high‐purity SP‐A/kg of porcine lung, as judged by gel filtration, SDS/PAGE and Western blotting. The electrophoretic profiles obtained showed that pure SP‐A consists of proteins of wide molecular mass in the range 26–36 kDa and a dimer in the range 56–60 kDa. The Western‐blot results displayed the same band pattern profile after incubating the membrane using a commercially available polyclonal anti‐SP‐A antibody produced in goat. Gel‐filtration experiments confirmed the molecular mass of SP‐A in 10 mM NaCl solution. The isolated SP‐A showed mannose‐binding ability, representative of its functionality.