Two young men required hospital treatment after being slashed on the face in Erskine.
A 20-year-old and 22-year-old man were in Bargarran Square around 10.50pm on Saturday July 7 when the attack took place.
The men suffered lacerations to the face after they were approached by two other men who then seriously assaulted them.
Both were taken to the Royal Alexandra Hospital for treatment.
Officers have been checking CCTV images from in and around the area for any additional information.
Detective Constable John Denholm said: “We are in the process of piecing together the details of this incident and establish a motive for the attack. There are a number of shops and business premises in this area and I am appealing to anyone who was in the area at the time to contact us, it’s possible they have information which could assist our enquiries.
"Anyone with information is asked to call CID officers in Paisley via 101, quoting incident number 5142 of Saturday 7 July 2018. Alternatively, please call Crimestoppers on 0800 555 111 where information can be given anonymously."