Objective Although many nursing home residents with dementia show agitation, hardly any literature is published about very frequent agitation. The WAALBED-III study focuses on the 2-week prevalence and correlates of very frequent agitation in these residents. Design Cross-sectional study using combined data of four studies. Setting One hundred nineteen dementia special care units in twenty-six nursing homes in The Netherlands. Participants Two thousand seventy-four residents with dementia. Measurements We operationally defined very frequent agitation as having a score of 6 (several times a day) or 7 (several times an hour) on at least five items of the Cohen Mansfield Agitation Inventory (CMAI) combined with a CMAI total score above the 90th percentile. To assess the association of demographic and behavioral characteristics with very frequent agitation, we performed a multivariate multilevel logistic regression analysis. Results The 2-week prevalence of very frequent agitation was 7.4% (95% CI: 6.374–8.634). Correlates for very frequent agitation were age (OR: 0.967, 95% CI: 0.942–0.992), dementia severity (GDS 6 = OR: 3.636, 95% CI: 1.929–6.875; GDS 7 = OR: 2.951, 95% CI: 1.321–6.588), delusions (OR: 2.480, 95% CI: 1.555–3.956), anxiety (OR: 1.904, 95% CI: 1.259–2.881), euphoria (OR: 3.712, 95% CI: 2.171–6.337) and irritability (OR: 4.411, 95% CI: 2.854–6.816). Conclusions To our knowledge, this study is the first to report prevalence data and correlates about nursing home residents with very frequent agitation. We found several correlated factors for very frequent agitation. Still, further research is needed for a better understanding of the behavior of this group, and to identify good treatment options.