Tropical forest ecosystems are threatened by habitat conversion and other anthropogenic actions.Timber production forests can augment the conservation value of primary forest reserves, but studies of loggingeffects often yield contradictory findings and thus inhibit efforts to develop clear conservation strategies. Wehypothesized that much of this variability reflects a common methodological flaw, simple pseudoreplication,that confounds logging effects with preexisting spatial variation. We reviewed recent studies of the effects oflogging on biodiversity in tropical forests (n = 77) and found that 68% were definitively pseudoreplicatedwhile only 7% were definitively free of pseudoreplication. The remaining proportion could not be clearlycategorized. In addition, we collected compositional data on 7 taxa in 24 primary forest research plots andsystematically analyzed subsets of these plots to calculate the probability that a pseudoreplicated comparisonwould incorrectly identify a treatment effect. Rates of false inference (i.e., the spurious detection of a treatmenteffect) were >0.5 for 2 taxa, 0.3–0.5 for 2 taxa, and