In this chapter we review numerous diagnostics capable of measurements at or near the first wall, many of which contribute information useful for safe operation of a tokamak. Infrared cameras, visible and vacuum ultraviolet cameras, pressure gauges and residual gas analyzers, thermocouples, and erosion and deposition measurements by insertable probes, quartz microbalances, and a rather extensive review of Langmuir probes are discussed. Also discussed are dust measurements by electrostatic detectors, laser scattering, visible and infrared cameras, and manual collection of samples after machine opening. In each case the diagnostic is discussed with a view toward application to a burning plasma machine such as ITER.