A urine collection bag formed of at least one flexible sheet of material defining a fluid reservoir is disclosed which includes an anti-reflux valve. The anti-reflux valve includes a housing defining a fluid receptacle which opens into the fluid reservoir. The housing is secured to the urine collection bag such that the opening of the receptacle is covered by the at least one sheet of material. A cut-out is formed in the sheet of material below the housing opening to define a flap which overhangs the opening in the fluid receptacle. The flap is movable into the fluid reservoir to allow fluid to flow from the receptacle into the reservoir. Fluid flow from the reservoir towards the receptacle causes the flap to seal against a peripheral rim of the housing and, thus, is substantially prevented.
