We study the microlocal analyticity of solutions u of the nonlinear equation u t = f ( x , t , u , u x ) where f ( x , t , ζ 0 , ζ ) is complex-valued, real analytic in all its arguments and holomorphic in ( ζ 0 , ζ ) . We show that if the function u is a C 2 solution, σ ∈ Char L u and 1 i σ ( [ L u , L u ¯ ] ) < 0 or if u is a C 3 solution, σ ∈ Char L u , σ ( [ L u , L u ¯ ] ) = 0 , and σ ( [ L u , [ L u , L u ¯ ] ] ) ≠ 0 , then σ ∉ W F a u . Here W F a u denotes the analytic wave-front set of u and Char L u is the characteristic set of the linearized operator. When m = 1 , we prove a more general result involving the repeated brackets of L u and L u ¯ of any order.