Viscous fingering is investigated by experiment in a 2-dimensional rad
ial Kele-Shaw cell and Monte Carlo stochastic simulation. Experimental
results show that viscosity ratio between the driving and driven flui
ds determines whether or not viscous fingerings occur and that surface
tension makes the viscous fingering patterns ''fatter''. Simulation p
atterns are in good agreement with experimental ones. The fractal dime
nsions of the viscous fingering patterns by both experiments and simul
ations are about D-f = 1.2 - 1.6.