This paper reports the ultrasonic measurements of the single-crystal second-order elastic constants and their pressure and temperature derivatives for a natural sample of pyrope garnet of composition (Mg0.61,Fe0.36,Ca0.02)3Al2Si3O12. Within the experimental precision of the pulse superposition method the pressure and temperature dependences of each of the three independent elastic constants were found to be linear in the range up to 10 kbar and from ambient conditions to 100¿C. The pertinent results for the adiabatic bulk modulus are Kps=1682.1¿3.6 kbar, (∂Ks/∂P) &tgr;=4.74¿0.16, and (∂Ks/∂T) &tgr;=0.188 ¿0.006 kbar/¿C, where each parameter is evaluated at 1 bar and 25¿C. These results are generally consistent with previous studies of the elasticity of pyrope garnet using high-pressure static compression methods: however, the present data have the advantage of increased precisin and accuracy. In addition, comparison of our results with corresponding data for other (Mg, Fe, Mn, Ca)3Al2Si3O12 garnets suggests that the specific type of the divalent cation in the eightfold coordination site has a relatively minor effect on the elastic properties of garnet, except for the Ca-rich end-member, grossularite.