Single‐mode experiments have been conducted on the Nova laser to examine the effect of perturbation shape on ablation front Rayleigh‐Taylor growth. The perturbations investigated had the same magnitude wave vectork=(k2x+k2y)1/2and the same initial amplitude. The shapes correspond to 2D &lgr;=50 &mgr;m, 3D squarekx=ky, and stretchedkx=3kyperturbations. We observed that the 3D perturbations grew more than the 2D perturbation. Numerical simulations in 2D and 3D are in agreement, showing the most symmetric modes growing the largest. ©1996 American Institute of Physics.