Sheath 50, 100 for an ultrasound probe 52 includes a sheath body 70 and an end cap 76. The sheath body is disposed about the probe 52 with the end cap 76 disposed about the end 57 of the probe 52. A band 78 is disposed about the body 70 in order to define between the end cap 76 and the band 78 a portion of the sheath 50 which can be expanded with fluid pressure in order to properly position the probe in a human cavity. The end cap 76 prevents fluid from expanding the end of the sheath 50. Alternatively a toroidal chamber 118 can be defined by a first cylindrical body 102 of the sheath 100 in combination with a second cylindrical body 116. A conduit 120 is provided externally to the probe 52 and sheath 100 for introducing fluid into the toroidal chamber 118.