Relative densities, (rho - rho(1) degrees), and heat capacity ratios, c(p) rho/c(p1)degrees rho(1) degrees - 1, for l-arginine, l-proline, and d,l-methionine in water have been measured at 288.15, 298.15, 313.15 and 328.15 K. These data have been used to calculate apparent molar volumes and apparent molar heat capacities. Calculated standard state volumes and heat capacities have been compared to available literature data. Standard state expansibilities have been calculated from the temperature dependences of standard state volume data.