We present the UV spectra of two quasars obtained with the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) prism (R $ 100). One quasar, at redshift z ¼ 3:5, shows an absorption edge consistent either with nearly fully ionized helium with an intergalactic He ii Ly optical depth at 304 8 of 304 > 3:1 (90% confidence), or a He iii region with edge 5.4 Mpc from the QSO. The spectrum of the second quasar, at z ¼ 3:8, has a broad absorption profile extending across the He ii emission line of the quasar consistent with a damped absorption profile from an intervening He ii system at z ' 3:7 with a column density of approximately 10 22 cm À2 . In this case, the extremely high He ii column density and absence of strong H i absorption suggests that the radiation field is quite weak at 4 ryd. The combined He ii and H i signatures are consistent with photoionization by a compact (1Y100 pc) star-forming region located approximately 10 Mpc from the quasar.

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