The troposphere, the lowest portion of the atmosphere, from Earth's surface to about 14 km, is a difficult region to probe from space. It is also an important region scientifically and for the welfare of the human race. So despite the difficulty, tropospheric sounding is a very important activity, and in the last 15 years or so, significant progress has been made. We are now able to derive tropospheric distributions of aerosols, carbon monoxide, nitrogen dioxide, ozone, and some other constituents from satellite data. Since many of the measurements are not straightforward, many new techniques have had to be developed and validated to determine their utility. Issues of the influence of the detailed radiative properties of the surface, cloud effects, stratospheric overburden, and the like have to be dealt with in a scientifically acceptable manner. Vertical resolution in these measurements is also poor; and the horizontal resolution, while improving, is still fairly low. Nonetheless, great progress has been made, and our understanding of some of the issues surrounding what can be loosely called pollution, on global and regional scales, has improved.