The expansion of the modified two-particle Ursell functionU(r) of a hardsphere quantal fluid is obtained in terms of a series of derivatives of δ-function. This expansion has been used to expand the second virial co-efficientB2 of the fluid. The expansion is correct up to the fourth power in thermal wavelength and the terms of the order of λ8 and λ4 in the first expa nsion are new.
