% to 0.8 gm% with Tween 80 concentration of 0.5% w/v and phase ratio of (1:2), particle size was increased from 390±9.4634 to 714±2.0548 and from 434±3.0912 to 863±0.9428 nm respectively. The same effect of polymer concentration on particle size was the same either in the case of increasing Tween 80 concentration and /or increasing the phase ratio as shown in the tables (4, 6 and 8) and figures (3, 5 and 7). When polymer concentration in the case of Eudragit S100 and HPMC Phthalate HP55 was increased from 0.2 gm% to 0.8 gm% with Poloxamer 407 concentration of 0.5% w/v and phase ratio of (1:2), particle size was increased from 404±8.6538 to 747±1.6997 and from 598±1.633 to 905±4.0277 nm respectively. The same effect of polymer concentration on particle size was the same either in the case of increasing Poloxamer 407 concentration and / or increasing the phase ratio as shown in the tables (5, 7 and 9) and figures (4, 6 and 8). These results were found to agree with the results of both Galindo-Rodriguez et al., 2004 [149] who prepared nanoparticles of Eudragit L100-55 using nanoprecipitation method to determine effect of polymer concentration on nanoparticle size using different organic solvents and he found that in all cases, increasing polymer concentration in organic phase resulted in increasing mean size [149],and D. Quintanar-Guerrero et al., 1999 [215] who used emulsion-diffusion method to prepare Eudragit E nanoparticles using Eudragit E/ethyl acetate/PVAL system and cellulose acetate phthalate (CAP) nanoparticles using cellulose acetate phthalate/2-butanone/Poloxamer 407 system and in two systems it was found that there is a switch between micro and nanoparticles depending on polymer concentration in internal organic phase where, as polymer concentration increased, size of produced particles significantly increased [215]. On the other hand, these results are disagreeing with those reported in Ahmed, I.S., et al.,2014 [216] who prepared poly-Ɛ- caprolactone nanoparticles by solvent displacement method and investigated the effect of polymer concentration on particle size. It was found that increasing polymer concentration from (0.5 to 0.8% w/v) at surfactant concentration (0.5% w/v) resulted in increasing particle size while, at the same surfactant concentration and increasing polymer concentration to (1% w/v) particle size decreased. Also, increasing polymer concentration from (0.5 to 0.8% w/v) at surfactant concentration (1% w/v) resulted in decreasing particle size while, at the same surfactant concentration and polymer concentration was increased to (1% w/v) particle size increased. These results were attributed >