Aggression is often associated with dementia. In this study, aggression in veterans newly diagnosed with dementia was examined and characterized. Participants were >or=60 years diagnosed with dementia at the Michael E. DeBakey Veterans Affairs Medical Center in Houston, Texas, from 2001 to 2004. Aggression was defined as a positive caregiver response to 1 or more of 3 probes from the Ryden Aggression Scale, administered during a telephone screen. Of 1276 contacts, 385 (30%) were eligible and agreed to participate; at initial screening, 75 (19.5%) were aggressive (23 [31%] verbally, 9 [12%] physically, 24 [32%] verbally and physically, and 19 [25%] with unspecified aggression). The surprisingly high prevalence of aggression in individuals newly diagnosed with dementia suggests the potential usefulness of early screening for aggression in this population.