We report the results of P-31 NMR measurements on YFe4P12, a new member of the family of the filled skutterudite compounds, which displays superconductivity below T-c = 7 K. In the normal state, the nuclear spin-lattice relaxation time T-1 obeys the Korringa relation T1T = constant below 40 K, but it changes its behavior at higher temperatures. The Korringa constant (T1T)(-1) for YFe4P12 is smaller than that for LaFe4P12, suggesting that the density of states at Fermi energy N(E-F) for YFe4P12 is lower than the case of LaFe4P12. In the superconducting state, T-1(-1)(T) shows a small coherence peak just below Tc, followed by an exponential decrease below 4 K revealing on energy gap 2 Delta(0)/k(B)T(c) = 3.3. Our results indicate that YFe4P12 is a conventional type s-wave superconductor. (c) 2005 Elsevier B.V. All rights reserved.