Ion sampling measurements have been made on cesium plasmas for normalized pressures from 10−4to 1 Torr using dc as well as rf excitation. For dc discharges, sampling was undertaken through both the anode and the cathode. The major cesium ions observed were Cs+,Cs2+, andCs3+. Measurements were made of the ion current ratios,I(Cs2+)/I(Cs+)andI(Cs3+)/I(Cs2+)as a function of normalized pressure. Comparison of the observed dependencies with those predicted using steady‐state kinetics provides estimates of the rate coefficients of the following reactions:Cs**+Cs→K2Cs2++e,K2&tgr;≃2×10−15 cm3,Cs++2Cs→&bgr;Cs2++Cs,&bgr;≃1.5×10−29 cm6/sec,Cs2++2Cs→&ggr;Cs3++Cs,&ggr;≃3×10−29 cm6/sec, andCs3++e→&agr;33Cs+h&ngr;3,&agr;3≃2×10−8 cm3/sec.