AbstractA method is described for dissolving and disaggregating chemically synthesized polyglutamine peptides. Polyglutamine peptides longer than about Q20 have been reported to be insoluble in water, but dissolution in – and evaporation from ‐ a mixture of trifluoroacetic acid and hexafluoroisopropanol converts polyglutamine peptides up to at least Q44 to a form readily soluble in aqueous buffers. This procedure also has a dramatic effect on peptides which appear to be completely soluble in water, by removing traces of aggregate that seed aggregation. The protocol makes possible solution studies—including in vitro aggregation experiments—on polyglutamine peptides with repeat lengths associated with increased risk of Huntington's Disease and other expanded CAG repeat diseases. It may also be useful in conducting reproducible, quantitative aggregation studies on other polypeptides.