Officers were called at 03.00 on Sunday 11 May to reports of a fight between two groups of men in Fore Street, N18 close to the junction with the A406.
Officers and London Ambulance Service attended and a 30 year old man was taken to hospital suffering from head injuries.
He is currently in a serious condition in hospital.
Six men have been arrested on suspicion of grevious bodily harm. One man has been arrested on suspicion of affray.
Detectives from Enfield are investigating.
Anyone with information are asked to call detectives on 0208 345 3311.