At least 30 members of Baltimore area police departments and the Maryland State Police have been called to active duty in the military since Iraq's invasion of Kuwait last August.
More than 300 others are subject to call-ups, police officials say.
The largest number of call-ups have been reported by the State Police. Eleven troopers, one cadet and a chaplain have left to report for assignments with Desert Shield, now Desert Storm.
"We estimate that about 100 agency members, sworn and civilian, have some sort of military obligation" and could be called up, said Maj. Morris L. Krome, assistant chief of the Services Bureau.
There are 1,700 sworn personnel and 600 civilian State Police employees statewide.
"The loss of any personnel certainly has an impact," he said. "But, fortunately, we're not talking about numbers which would severely impact the State Police and its services to the community."
Baltimore City police officials said 12 department employees have been called up since August, including one who was to report for duty today after graduating from the department's training academy.
Police spokesman Dennis Hill said the 12 have come from "everywhere in the department . . . from clerks to uniformed officers." Most are men.
None of the call-ups will affect police protection in the city, Hill said. "Citizens should never see any difference."
There are 3,400 police employees in Baltimore, 2,875 of them uniformed officers. Of those, 140 are subject to call-ups for active military duty.
In Baltimore County, police spokesman Sgt. Stephen R. Doarnberger said four department employees have been called up, one of them female. Three are with the 290th Military Police Company, from Towson. One is with the 29th Air Traffic Control Unit in Edgewood.
An additional 64 Baltimore County police employees are subject to possible call-ups, from a department of 1,840.
The 250-member Harford County Sheriff's Department reported only one employee has been called up. He left Saturday for duty with the Marine Reserves.
Howard County media relations spokesman Gary Gardner said none of that county's police employees have been called up yet.