New daily persistent headache (NDPH) is a subtype of chronic daily headache. The literature on NDPH is scant and its true aetiology is unknown. A retrospective chart review was carried out from a computerized database at the Jefferson Headache Centre from August 1997 to May 2000 to identify patients with NDPH using the Silberstein et al. criteria. Forty women and 16 men were identified. Age of onset ranged from 12 to 78 years. The peak age of onset was the second and third decade in women and the fifth decade in men. Eighty-two per cent of patients were able to pinpoint the exact day their headache started. Onset occurred in relation to an infection or flu-like illness in 30%. A prior headache history was found in 38% of patients. A family history of headache was documented in 29%. The duration of daily headache ranged from 1.5 h to 24 h; 79% were continuous. Nausea occurred in 68% of patients, photophobia in 66%, phonophobia in 61%, and lightheadedness in 55%. Laboratory testing and neuroimaging in all patients was normal except for Epstein-Barr virus antibody titres, which were positive in 71% of seven patients tested, representing past infection. NDPH appears to be a female-predominant disorder, marked by a continuous daily headache with associated migrainous symptoms. Over 80% of patients could state the exact date their headache began. One-third of patients developed NDPH with a flu-like illness.