To test the association between arcuate foramen (AF) in the first cervical vertebra with acute headache attributed to whiplash. Retrospective study of 128 patients that suffered a whiplash. The presence or absence of AF was recorded after a radiographic study, as well as the presence or absence of acute headache after the whiplash. The frequency of AF was 17.2%. Patients with bilateral AF presented a significant (p = 0.000, Fisher's test) increase in the frequency of acute headache (90.9%) in comparison with the non-AF group (5.7%). The ratio between the presence and absence of acute headache was 166.6 times higher (IC 95% 18.2-1526.22) in subjects with bilateral AF in comparison with non-AF subjects. The presence of bilateral AF is associated to an increased frequency of acute headache after suffering a whiplash, information of interest for the attention to these patients.