Abstract: This quasi-experimental study tested if psychological trauma accumulates and if so what model best describes that accumulation. Police officers were the focus of the study. There were 438 participants including 180 San Diego Police, 97 Wyoming Police and 161 civilians. A vignette methodology was used. Nine vignettes designed to simulate traumatic exposure of a police officer were given to participants to rate. Vignette booklets varied by the order of the most traumatic vignette and the initial trauma level of the officer described in the vignette booklet. The results indicated that psychological trauma demonstrates a significant accumulation over multiple exposures. An exponential model was predicted, however a cubic model was the most descriptive model of this accumulation. There were no significant differences between urban and rural police demonstrated. Non-police rated the vignettes significantly higher than police. The order of the most intense vignette did not affect the rating of the other vignettes. A high initial trauma condition of the fictitious officer described in the vignette booklet did cause participants to rate the vignettes significantly higher than the low trauma initial condition. The study found that trauma does accumulate. It suggests that frequency of exposure rather than a single high intensity event may account for that accumulation. The study suggests that frequency of exposure or an additive model may be the most explanatory model rather than a sensitization model. This implies that intervention for trauma should be based on the frequency of exposure rather than exposure to a single high intensity event.