The in vivo effects of Fructus Benincasae (FB-Baekdongkwa(B) and FB- on the expectoration (decrease in sputum viscoelasticity) by their sorts and using rats (Sp. D. male, $150{sim}160g$). FB was divided by seed, flesh, and bark, extracted by 95% ethanol for 3 hr. The extracts were given to rats administration and the following results were obtained: 1. When FB Recens-C extract was administered at the concentration of 300 mg/kg b.w., mucus secretion effect in the trachea was desirably stimulated. 2. The secretion of phenol red was increased in the FB-treated tracheas in the order of Semen Benincasae(SB)-B $(153{pm}8;%)$, FB-B $(149{pm}10;%)$, and FBR-C $(117{pm}26;%)$. In general, the effect of FB-B extract on phenol red secretion was stronger than that of FB-C. 3. When tracheobronchial lavage fluid was analyzed, the mucus secretion was relatively high $(111{pm}14;%)$ in FB-B compared with other extracts. 4. Microscopic analysis after direct treatment of the FB extracts to the rat tracheal tissue showed that all the FB extracts possessed no effects for the activity of the ciliary movement. 5. Glycoprotein content secreted by the seed extract of FB-B was increased compared with the control group, which represents the highest secretion effect of mucus. From the above results. we could conclude that the seed of SB-B possesses better activity for mucus secretion from trachea than the extracts of any other parts. Therefore, it is expected that the seed of SB-B may be available for the purpose of expectorant activity in the prescription of traditional medicine.