4, 6-Disubstituted N-(3-piperidinopropyl)furo[3, 2-b]indole-2 carboxamide derivatives possess analgesic and antiinflammatory activities. To understand how substituents affect the biological activities, the quantitative structure-activity relationships of 26 compounds were analyzed by the adaptive least-squares method. For analgesic activity, the steric effect of the substituent at the 6th position in terms of the STERIMOL length and width parameters needs to be augmented to obtain higher activity. For antiinflammatory activity, an electron-donating effect of the substituent at the 6th position seems to be favorable. On the other hand, the physicochemical factors relating to the role of the 4-substituent were not clarified. A similar correlation was obtained by Hansch analysis of analgesic ED₅₀ values of 21 derivatives in mice.