A study has been made of available experimental data for the cross section and fission parameters for U233. These data have been used to arrive at recommended values of the parameters for 2200 m/sec neutrons as follows: σnT = 586 ± 2 b; σn,n = 13 ± 3 b; σnX = 573 ± 4 b; 1 + α = 1.0935 ± 0.0038; σn,f = 524 ± 4 b; σn,γ = 49 ± 2 b; η = 2.291 ± 0.009; 2.50 ± 0.012. The methods used in deriving the recommended values are presented in detail and brief summaries of the measurements are included. Energy dependent absorption and fission data from 0.02 to 1 ev that have recently become available are presented.