Objectives: To determine whether specific external signs of emotional distress (ESED) can be an indirect measure of emotional distress in caregivers.; Methods: A cross-sectional multicentre design was used. 148 primary caregivers of advanced cancer patients attended in four Spanish palliative care units participated in this study. The emotional distress of caregivers was measured using both the Emotional Distress of Caregivers Scale and a psychological interview. Health professionals collected data using a standard clinical interview process after a brief training period.; Results: More than half the caregivers (60%) presented with emotional distress. A positive correlation (r=0.566) was found between the intensity of ESED and emotional distress per se. Caregivers who presented emotional distress showed more ESED than those that did not (p<0.01). The study found significant differences for the categories 'visible signs of sadness, fear, crying, feeling overwhelmed' (p<0.001), 'difficulty in separating from the patient: family refuses to let the patient make decisions and insists on care' (p<0.001) and 'visible signs of anger, irritability or frequent disagreement with therapeutic measures' (p<0.001). No significant differences were found with respect to gender. The set of items to measure these external signs presented an adequate reliability assessed using Cronbach's alpha (α=0.773).; Conclusions: The assessment of ESED in caregivers could serve as a useful method to assess their emotional distress. Incorporating the systematic assessment of these external signs as part of the assessment of the emotional distress of primary caregivers could improve the overall assessment and treatment provided to these caregivers.