Shortcomings in attributing effect on children mortality Jaime Chang, Personal 27 October 2008 No data on risk factors for malaria other than “presence of bednet with probably insufficient insecticide to be considered as an ITN”. No data on risk factors for other causes of child mortality are collected either.Socioeconomic features included in analysis are not risk factors and therefore should not be considered confounding factors or explanatory variables. Although reasonable, the assumption of homogeneous composition of population among all villages is made but not stated (no adjustments made).“Bednet density” should not be considered a “measure of the impact of bednets” but an indicator for ownership (an indicator for utilization would imply other variables). Information provided does not support the statements “density of household bed net ownership was the only factor significantly associated with child mortality reduction” and “The spatial effects of bednets on all-cause child mortality in an area of high perennial malaria transmission in southern Tanzania have been presented here.” At best, an association is shown without evidence presented on a cause-effect relationship.Authors acknowledge that “a limitation of our study consists in linking child mortality data across 2 years (2001 - 2003) with data on mosquito net ownership collected at a single time point (2002)” but do not explain how it was dealt with or how could it affect the study and its results.Comparison with results from studies measuring community effect of ITNs seems inappropriate given that this study does not measure effect of ITNs. Magnitude and uniformity of bednet presence in households in the communities hinder possibility of comparisons for areas of even small radius (information provided by authors support this). It would be interesting to know if in the same study population the “bednet density” actually performs better than other indicators utilized for representing bednet presence and/or use. Competing interests None. Please note this is a personal comment and does not represent an institutional position.