The results of an extensive model testing program of helical piles with single, double and triple cylindrical screw helixes installed in sand are presented in this paper. A total number of sixty three model pile load tests were carried out including uplift tests on single and pile groups. A set of tests was performed at fixed helix spacing, embedement depth, number of helixes and helix diameter with different number of piles and pile's spacing to evalute group efficiency. The test results showed that the axial uplift resistance for helical pile increases as embedement ratio (H/R) increases. For the same embedement ratio (H/R), a gain in the axial uplift resistance for the pile constructed in sand increased as the sand relative density increased. Significant positive effect of number of helixes on the axial uplift resistance of the helical piles was observed. As the helix diameter increases, the axial uplift capacity increases. Also, the rate of incease in the uplift capacity increased as the sand relative density increased. The sand relative density has significant effect on the efficiency of pile groups. In the case of loose sand, the efficiency approaches 100% in the case of 3 helixes diameter spacing, while this value of efficiency was found to be less than 100% and exceeds 100% for helixes spacing 2, and 4 helix diameters respectively. In case of medium and dense sand, the eficiency of pile groups was found to be less compared with the efficiency of the same pile group in loose sand. Finally, the group efficiency was found to decrease as the sand relative density increased. The group efficiency increases as pile spacing and number of piles increase in the group.