The aim of this study was to estimate the prevalence of primary insomnia in female family caregivers of totally dependent patients with dementia, and to examine the relation between this sleep disorder and a number of characteristics of the caregivers, care recipients, and caregiving situations. The participants were 134 female caregivers, who answered a diagnostic interview according to DSM-IV-TR diagnostic criteria. The functional status of the dependent person was assessed through the Barthel Index, and sociodemographic and related caring variables were collected through an ad hoc questionnaire. The prevalence of primary insomnia was 41.0%. Caregivers over 55, with more than eight years providing care and more than 12 daily hours of care, had a higher risk of developing insomnia. Multivariate analysis through binary logistic regression analysis showed that the factors more strongly associated with this diagnosis were the years of care duration (Wald= 4.02, p= .045, adjusted OR= 2.12, 95% CI= 1.02-4.42) and the daily hours of care (Wald= 4.07, p= .044, adjusted OR= 5.01, 95% CI= 1.05-23.92). Health care professionals should carefully check sleep complaints in female caregivers.