This paper has investigated the flow interference between three circular cylinders of equal diameter in an equilateral-triangular arrangement and also between four circular cylinders in a square arrangement when subjected to a cross-flow. Wind tunnel experiments were conducted to measure force coefficients for six spacing ratios (l/d) varying from 1.5 to 4 at subcritical Reynolds number of 6.08×104. The pressure distributions on the surface of the cylinders were measured, using pressure transducers. It was found that for three cylinders at l/d>2, the upstream cylinder experiences lower mean drag coefficient than that of the downstream ones. Also, the minimum drag coefficient values of the downstream cylinders occur at l/d=1.5 and l/d=2. Moreover, It was revealed that for four cylinders at l/d=1.5, due to severe flow interference between cylinders, there is a difference between lift coefficients for the upstream cylinders. Also, for l/d£2, the mean drag coefficients for downstream cylinders are negative. In addition, it was concluded that the variations in l/d strongly affect the aerodynamic coefficients. Also, by decreasing l/d, the effects of the flow interference between the cylinders increase.