The miticidal activities against the house-dust mite, Dermatophagoides pteronyssinus, of the leaves, bark and twigs of fig trees (Ficus carica L) were studied. The leaves showed the strongest activity among the three parts, and the activity was dose dependent. The larger the weight of each part, the higher the miticidal activity was. Miticidal activities of coumarin homologs were also studied. Coumarin homologs that have substituents on the coumarin skeleton showed lower miticidal activities than coumarin, suggesting they will not easily make contact with mites because of steric hindrance of bulky substituents. The α-Pyrone skeleton of coumarin homologs is important to have high miticidal activity and the benzene skeleton condensed to　 α-pyrone contributes to miticidal activity. Psoralen which has a furan ring condensed to coumarin skeleton, showed also high miticidal activity. Saturated lactones such as γ-butyrolactone, γ-valerolactone and δ-valerolactone have weaker miticidal activities than cyclotene, maltol and crotonic acid which have the α-, β-unsaturated carbonyl system.