Many international development agenciesand some national governments base future budget planningand policy decisions on a systematic assessment of theprojects and programs in which they have already invested.Results are assessed through Mid-Term Reviews (MTRs),Implementation Completion Reports (ICRs), or through morerigorous impact evaluations (IE), all of which require thecollection of baseline data before the project or programbegins. The baseline is compared with the MTR, ICR, or theposttest IE measurement to estimate changes in theindicators used to measure performance, outcomes, orimpacts. However, it is often the case that a baseline studyis not conducted, seriously limiting the possibility ofproducing a rigorous assessment of project outcomes andimpacts. This note discusses the reasons why baselinestudies are often not conducted, even when they are includedin the project design and funds have been approved, anddescribe strategies that can be used to'reconstruct' baseline data at a later stage inthe project or program cycle.