The crossing porous structure of InP has been obtained by electrochemical etching in NaF solutions. The behavior of the periodic oscillation occurs at different potential ranges for the different concentrations of solutions, and it will disappear with the concentration of the solution decreased. The scanning electron microscope (SEM) image shows that the pores have two directions on the surface and are perpendicular to each other. The two directions are assigned to [0 1 1] and [0 (1) over bar 1], respectively. The SEM image of the cross-section also shows that the two directions are assigned to [1 1 1] B and [1 (1) over bar (1) over bar] B. Both are due to the selective etching of F ions. The crossing porous structure of InP is a very promising feature for the three-dimensional structure of III-V compound semiconductors for photonic band gap materials. (C) 2009 Elsevier B.V. All rights reserved.