Yolk specimens from chicken ovaries during oogenesis gave a positive signal for ovalbumin as analyzed by Western blotting, indicating that the ovarian yolk contains ovalbumin. Northern blotting and reverse transcriptase-polymerase chain reaction gave a negative signal for ovalbumin mRNA in the liver and other organs except oviduct, whereas the laying hen serum was found to indicate immunologically the presence of ovalbumin. It was therefore assumed that ovalbumin synthesized in the oviduct might partly be secreted into the blood circular system, from which it is taken up into the oocyte.