Behavioral and psychological symptoms of dementia (BPSD) are characterized by fluctuations in their frequency and severity as well as by differences in the concurrent presentation of different symptoms. The goal of the current study was to identify groups of patients with Alzheimer's disease (AD) that had similar trajectories in the expression of BPSD. Over a 24-month period, an observational study was conducted using a population of ambulatory patients with AD of mild or moderate severity. The Neuropsychiatric Inventory (NPI) was administered every 6 months to the patient's caregiver. To classify patients according to changes in the frequency and severity of BPSD, growth mixture models were fitted to the applied to the grouping of NPI subscales in the following three categories: psychotic syndrome (hallucinations and delusions), affective syndrome (depression, anxiety, irritability, and agitation), and behavioral syndrome (disinhibition, euphoria, apathy, and aberrant motor behavior). The sample population consisted of 491 patients (70.9% women) that had an average age of 75.2 years (SD=6.6). Different trajectory patterns were identified based on differences in changes over the time in the frequency (stable, increasing, decreasing, or fluctuating in course) and severity (low, moderate, or elevated severity) for psychotic syndrome, emotional syndrome, and behavior syndrome. Patients with AD display a high degree of variability in the evolutionary course of BPSD. It is possible to identify groups of patients with similar evolutionary trajectories in terms of changes in the frequency and severity of BPSD.