Sol-gel syntheses of nanoparticle titania commonly results in a mixture of anatase and brookite. Hydrothermal aging is a commonly performed post-sol-gel synthesis step, which generally results in a more crystalline product and larger crystallites. This work investigates the effect of increasing ionic strength on the phase composition of hydrothermally aged titania. Rietveld refinements were used to systematically track the brookite content and both anatase and brookite particle size. Results demonstrate that increasing ionic strength during hydrothermal aging has no effect on brookite content. The presence of chloride is concluded to have the most influence over the brookite content during the solgel synthesis and that the addition of chloride to chloride-free, solgel synthesized titania has no effect during hydrothermal aging. Photocatalysis results using particles of similar size but different phase composition suggest that particles with higher brookite content are less photocatalytically active than those with lower brookite content. Results suggest that substantial control over photocatalytic activity of titania nanoparticles can be achieved by modifying sol-gel synthesis conditions. copyright The Electrochemical Society.