In this paper, we consider a uniform elliptic nonlocal operator
scriptAαu(x)=Cn,αP.V.∫Rna(x−y)(u(x)−u(y))|x−y|n+αdy,
which is a weighted form of fractional Laplacian. We firstly establish three maximum principles for antisymmetric functions with respect to the nonlocal operator. Then, we obtain symmetry, monotonicity, and nonexistence of solutions to some semilinear equations involving the operator
scriptAα on bounded domain,
double-struckR+n and
double-struckRn, by applying direct moving plane methods. Finally, we show the relations between the classical operator − Δ and the nonlocal operator in () as α→2. Copyright © 2016 John Wiley & Sons, Ltd.