BPSD are very frequent, so that 90% of demented patients have at least one. BPSD are troublesome both for elders with dementia and for caregivers, fostering the institutionalization. Yet, BPSD may vary as long as the disease progresses, and may fluctuate in the short run, either spontaneously or by pharmacological as well as non-pharmacological interventions. The aim of the study was to investigate by factor analysis possible groupings among the modifications occurring in BPSD, during the stay in a special care unit (SCU). BPSD were rated through the neuropsychiatric inventory (NPI); frequency x severity scores were calculated for any single BPSD at entry and at discharge: the differences were analyzed using factor analysis. The sample comprised 214 demented persons, 65.4% females; of mean age 79.6 years; Overall entry score of NPI was 46.1+/-20.7; NPI overall mean difference at discharge=-30.4+/-20.3. BPSD factor analysis on frequency x severity crude baseline scores resulted in 4 groups: 1 (agitation+irritability+aberrant motor activity+disinhibition); 2 (delusions+hallucinations); 3 (anxiety+dysphoria); 4 (apathy+euphoria). When differences (discharge frequency x severity-entry frequency x severity) for each BPSD scores were factor analyzed, grouping was rather similar: (i) agitation+irritability; (ii) delusions+hallucinations; (iii) anxiety+dysphoria+aberrant motor activity; (iv) euphoria+disinhibition; (v) apathy. In our sample, BPSD improved during the stay in the SCU. These improvements followed trajectories that looked plausible and were consistent with baseline groupings, by factor analysis.