The average dimensions of poly(amido amine) (PAMAM) dendrimers of generations G5 and G8 are studied by small-angle neutron scattering (SANS) asa function of solvents of differing quality, the composition of mixtures of a good solvent and a nonsolvent, and temperature. The radius of gyration, R-g, of the G8 dendrimer decreases for the series of solvents D(CD2)(m)OD (with m = 0, 1, 2, 4) by approximately 10% from m = 0 to m= 4 with decreasing solvent quality. The average segment density in solution is calculated for G5 and Gs. The size of PAMAM dendrimers, as reflected by R-g, is not influenced by the composition of mixtures of methyl alcohol/acetone in the full range of solubility of the dendrimers. In the temperature range =10 degrees C less than or equal to T less than or equal to 50 degrees C,the dimensions of the G8 and G5 dendrimer are constant, within approximate to 5% of each other.