Fatigue testing was performed on three austenitic stainless steels in tension-tension in distilled water and in Ringer's solution at 37°C using an MTS servo-hydraulic testing system following the guidelines of ASTM F1801. The materials chosen were BioDur® 108, BioDur® 316LS and BioDur® 22Cr-13Ni-5Mn stainless steel. Samples with a 2.5 mm diameter in the gauge length of 10 mm were prepared from 8 mm diameter bar stock using low stress grinding techniques. A minimum of three samples at each of five load levels were cycled to failure or to a maximum of 106 cycles. S/N curves for each material under each condition were plotted and fracture surfaces were examined using scanning electron microscopy (SEM). Comparison between the fatigue response of each material in distilled water and Ringer's solution as well as between alloys was evaluated. Results showed typical S/N curve response comparison of stainless steels in distilled water vs. salt solutions with curves slightly shifted in a positive direction (higher numbers of cycles to failure at equal stress values) in distilled water as compared to Ringer's solution. Additionally, although not statistically evaluated, the fatigue curves were shifted toward higher numbers of cycles to failure for the two nitrogen strengthened alloys with the number of cycles to fracture for 22Cr-13Ni-5Mn being slightly higher in distilled water at lower stress values and the fatigue curves for 22Cr-13Ni-5Mn and BioDur® 108 in Ringer's solution were essentially equivalent. Evaluation of fracture surfaces by SEM showed variations in fatigue striation spacing as a function of loading in all alloys. A difference in fracture morphology of the BioDur® 108 was noted near the area of crack initiation as compared to the other two alloys. Flutes and terraces, not normally seen in fatigue of austenitic stainless steels at in vivo temperature, were seen.