A confidential notice has been issued to soldiers at Catterick Garrison, North Yorkshire, urging them to take an immediate HIV test, a spokesman said last night.
He added that the army had confirmation that two women civilians living near the garrison were carrying HIV.
The "Special Routine Order", issued last Wednesday and signed by the deputy commander of Catterick Garrison, Colonel Neil Donaldson, states: "It has been reported by a confidential source that at least two females living in the geographical area of Catterick Garrison have contracted the Aids virus and are HIV positive.
"The same females are believed to be liberal with their affections, particularly to soldiers, and are not adverse to indulging in casual sex, often unprotected.
"All ranks are reminded that there is no known cure for Aids. In short, it is a killer.
"If you have had casual sex in this area you are strongly advised to seek the advice of your medical officer without delay."
It is thought that more than 100 men have sought medical advice since the order was issued.
The garrison has 5,500 military personnel, but at the moment only one regiment is stationed at the base. Four are on service in Bosnia and two in Northern Ireland. The personnel in those regiments are not thought to have received the warning yet.
The spokesman said he was unable to confirm reports that one of the women believed she had been infected by a soldier and was taking part in a revenge sex spree.
Soldiers are being offered medical tests and counselling at a confidential clinic within the garrison.
One source described the rush of soldiers attending the centre as "a stampede".
A statement released by the garrison last night said: "The Army has a duty of care to its personnel to warn them of the possible health risks and hence we have issued both verbal and written warnings.
"The advice given is that anyone who believes they may have been exposed to risk should seek medical advice and if necessary arrange for confidential testing to be carried out."