Background: Although the incidence of sudden unexpected infant death (SUID) has decreased since the 'Back to Sleep' campaign in English-speaking countries and other preventive campaigns, the circumstances of such deaths remain unclear. Aim: To analyse infant deaths recorded at the referral centre for sudden infant death of the West Provence-Alpes-Côte d'Azur region of France (West PACA) and the forensic medicine department of Marseille University Hospital. Methods: Information on all SUID cases from 2000 to 2017 was extracted from the referral centre for sudden infant deaths in West PACA and the forensic medicine department of Marseille. Results: The study included 130 infants over the 17 years with a very similar distribution. There was a marked male preponderance, with 61.6% of boys whatever the age at death (sex ratio 1.6). Half of the deaths occurred in the first 6 months of life and the majority (61%) of infants died during autumn and winter. Nearly one-third (33.2%) had presented with minor infections and 21% had been seen by a doctor or had been admitted to hospital. Most deaths (86.4%) occurred during sleep (night or day). Nearly half of the infants (47.7%) were discovered in a prone position. A large majority of parents (90.7%) agreed to a post-mortem examination. Only 6.2% of deaths led to legal proceedings. Nearly 16.9% remained unexplained after compiling all the data included in the protocol and 9.2% remained unexplained because of incomplete investigation, including refusal of post-mortem examination. Abuse was involved in 2.3% of cases. Conclusions: Asymptomatic infectious conditions were associated with a high proportion of SUID cases. Non-supine sleep positions were still practised. There is a need to increase SUID prevention campaigns. Abbreviations: HAS, Haute Autorité de Santé: French National Health Authority; NICHD, National Institute of Child Health and Human Development; PACA, Provence-Alpes-Côte d'Azur region of France; SUID, sudden unexpected infant death; SIDS, sudden infant death syndrome; CépiDc, Centre d'Epidémiologie sur les Causes Médicales de Décès/Center for Epidemiology on the Medical Causes of Death.