We introduced the concepts of fluctuations and dissipation in Chap. 2, where we discussed the approach of a chemical system to a nonequilibrium stationary state; we recommend a review of that chapter. We restricted there the analysis to linear and nonlinear one-variable chemical systems and shall do so again in this chapter, except for a brief referral to extensions to multivariable systems at the end of the chapter. In Chap. 2 we gave some connections between deterministic kinetics, with attending dissipation, and fluctuations, see for example (2.33), which equates the probability of a fluctuation in the concentration Xto the deterministic kinetics, see (2.8, 2.9). Here we enlarge on the relations between dissipative, deterministic kinetics, and fluctuations for the purpose of an introduction to the interesting topic of fluctuation dissipation relations. This subject has a long history, more than 100 years [1, 2]; Reference [1] is a classical review with many references to fundamental earlier work. A brief reminder of one of the early examples, that of Brownian motion, may be helpful.