In the years of the Einstein and ASCA satellites, it was known that the total hard X-ray luminosity from non-AGN galaxies was fairly well correlated with the total blue luminosity of the host galaxiy. However, the origin of this hard component was not well understood. Some possibilities that were considered included X-ray binaries, extended upscattered far-infrared light via the inverse-Compton process, extended hot 10⁷ K gas (especially in ellipitical galaxies), or even an active nucleus.

Now, for the first time, we know from Chandra images that a significant amount of the total hard X-ray emission comes from individual X-ray point sources. I will present analyses of Chandra data for X-ray point sources in a sample of ~40 galaxies, including both spiral galaxies (starbursts and non-starbursts) and elliptical galaxies. I will discuss the relationship between the X-ray point source population and the properties of the host galaxies. We show that the slopes of the point-source X-ray luminosity functions are different for different host galaxy types and discuss possible reasons why.

I shall also discuss X-ray properties of very luminous X-ray point sources known as "Intermediate-luminosity (between X-ray binaries and AGNs) X-ray Objects" (IXOs), or ULXs. These objects have been widely publicized as being accreting intermediate-mass (100-1000 Msol) black holes, although they may be anisotropically emitting "normal" X-ray binaries.