Four men from Maidenhead have been arrested on suspicion of GBH in Reading.
They, and another man from Taunton in Somerset, were arrested following a fight in the Broad Street area early on Sunday morning which left a 24-year-old man seriously injured.
The man from Woosehill near Wokingham was taken to hospital and has been diagnosed with a bleed to the brain.
He remains under close observation.
The five men, all aged between 19 and 21, have been bailed to appear at Loddon Valley Police Station on April 22.
Witnesses have been urged to call police on 101.
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The victim of an assault in Cippenham was flown to hospital by air ambulance this afternoon.
A rapid response vehicle, an ambulance officer, an air ambulance and an ambulance crew were all called to an address in Earls Lane at 2.10pm.