Models of the female urethra have been constructed, each consisting of a distensible tube with a pressure maximum or elastic constriction near its midpoint. By measuring by two different methods the relation between the fluid pressure and the cross-sectional area at the elastic constriction, we have tested the assumption, important in the understanding of flow through such tubes, that the pressure in the tube depends only on the local cross-sectional area. The assumption is valid for elastic constrictions characterised by a broad pressure maximum, but becomes increasingly incorrect as the pressure maximum is progressively more sharply localised. Clinical data suggest that it may not be correct for the resting female urethra. In addition, the indirect Brown-Wickham method of measuring intra-urethral pressure, often used clinically, is found to be accurate within ±2 cm H2O in the model urethra.