We have used the CFHT and Gemini South telescopes to obtain high-resolution, high signal-to-noise optical and near-infrared spectra of several lines of neutral helium in a number of helium-peculiar, HgMn and related stars. Since the helium lines observed have 3He isotope shifts of up to 1 Å and sample a large range of continuous opacities in the program stars, these spectra are being used to search for the presence of 3He in their photospheres and, where 3He is present, examine the possible stratification of both isotopes of helium in their atmospheres. Analysis of a number of previously identified 3He stars provides strong evidence for different vertical stratification profiles of 3He and 4He in these stars. 4He is generally enhanced deep in the photospheres but sharply depleted high in the atmospheres while 3He appears to be confined to a narrow layer above the 4He.