Police were today called to reports a man had been injured in Marshall Street.
The victim, who is said to have injuries consistent with being stabbed, has been taken to hospital.
Police said one person had been arrested, but did not give an age for the male suspect.
Eyewitnesses have said police cars and vans can be seen on the street.
More details are expected to follow.
A spokeswoman for West Yorkshire Police said: "Police were called to reports of a man injured on Marshall Street in Crossgates, Leeds.
"A man was taken to hospital with injuries consistent with stab wounds.
"A male has been arrested in connection with the incident.
"Enquiries are ongoing."