Positron lifetime and Doppler line-shape studies have been made on helium-implanted (100 appm) titanium-stabilized austenitic stainless steels (TiSS), following two different preirradiation sample treatments. For both TiSS1 (solution-annealed sample) and TiSS2 (solution-annealed plus cold-worked plus aged sample), the variation of line-shape parameter Iv as a function of postirradiation annealing temperature exhibits an initial decrease, a broad shoulder between 670 and 970 K, and a final sharp fall beyond 1000 K. The lifetime τ2 shows a minimum at 670 K, beyond which it increases sharply accompanied by a decrease of its intensity I2 for both TiSS1 and TiSS2. The near-saturation value of τ2 at the higher annealing temperature for TiSS2 is found to be lower than that for TiSS1. The lifetime results of TiSS1 are explained as due to the nucleation and growth of helium bubbles formed at substitutional titanium complexes, while the results of TiSS2 are understood as due to nucleation and growth of bubbles at fine TiC precipitates. From an analysis of bubble parameters based on the experimental data for both TiSS1 and TiSS2, and their comparison with those of titanium-free SS316 steel, significant bubble size reduction and enhanced bubble density are indicated upon titanium addition. Above 1000 K, a third long lifetime component of weak intensity is observed for both TiSS1 and TiSS2, which might suggest bubble ripening with a bimodal distribution.