Abstract: A seal apparatus (40) for sealing between relatively rotatable structures (12,14) is provided and has a pair of seal rings (62,64) which are engageable at axial sealing face portions (70,72). Axially facing surfaces (78,80) of the first seal ring (62) are arranged such that fluid pressure acting thereon biases it in a first direction. Axial positioning and circumferential retention of the second seal ring (64) is provided by an elastomeric toric (68) which is arranged radially between the second seal ring (64) and a retaining ring structure (46) which constitutes a part of the relatively rotatable structure (14). Axially facing surfaces (82,84,96) of the second seal ring (64) and the sealing toric (68) have areas in the axial direction which cause the second seal ring (64) to be pressure balanced in the axial direction by fluid pressure exerted thereon.