Data about participants from before a program can be collected either prior to the program (prospective or true pretest) or after the program (retrospective pretest). There are pros and cons to both types of pretest. Retrospective pretests are typically used when logistics prohibit collecting data about participants before the program, or when there is a worry that participants may not fully understand the subject matter before an intervention (i.e., response-shift bias). However, retrospective pretests may introduce their own sets of biases, such as recall bias. For example, participants may remember their former state as better or worse than it actually was, or similar to how they are currently feeling. This presentation presents true pretest, retrospective pretest, and posttest data collected from a multi-year evaluation study to demonstrate the differences between both types of pretest. Recommendations are offered for choosing pretest methods and using them appropriately in our evaluation work.Presented with Tom McKlin and Han Hao of The Findings Group.