Summary The UAS-A42 H29.3 transgenic Drosophila line used to model Alzheimer type neurodegeneration and other phenotypes falls down when transitioned from a light to a dark environment. This unusual phenotype is not dependent on the presence of a Gal4 driver and is thus unrelated to A42 induced proteotoxicity or neurodegeneration. We propose that it may instead be the result of disruption in another gene function caused by the P element insertion site. Since this transgenic line is used by several groups to analyze neurological phenotypes associated with A42 neuronal expression, the results of these studies must be interpreted with caution.