Aims: To describe uptake and retention of pathogenic and nonpathogenic Vibrio parahaemolyticus in Ruditapes decussatus and Ruditapes philippinarum. Methods and Results: Ruditapes decussatus accumulated greater concentrations of pathogenic and nonpathogenic V. parahaemolyticus than R. philippinarum. These concentrations decreased earlier in R. decussatus. Nonpathogenic V. parahaemolyticus reached higher concentrations (approx. 1 log CFU g(-1) in tissues of R. decussatus and more than 1 log CFU g(-1) in R. philippinarum) than pathogenic V. parahaemolyticus at similar times. It also persisted longer in both species of clams (72 h in R. decussatus and 96 h in R. philippinarum), while pathogenic V. parahaemolyticus persisted 48 h in R. decussatus and 72 h in R. philippinarum. Conclusions: Ruditapes decussatus incorporated both isolates of V. parahaemolyticus faster than R. philippinarum and it eliminated both isolates earlier than R. philippinarum. Under same conditions, nonpathogenic V. parahaemolyticus might survive better than pathogenic V. parahaemolyticus within both species of clam. Significance and Impact of the Study: Pathogenic V. parahaemolyticus is an important cause of foodborne illnesses. This study shows it may be possible to use nonpathogenic V. parahaemolyticus to perform experimentation to evaluate bacterial evolution in clams, developing an in vivo model useful for risk analysis.