This study demonstrated online monitoring of hydroxide, or effective alkali (EA), sulfide, and dissolved lignin in kraft wood pulping processes using flow injection analysis (FIA) and attenuated total reflection (ATR)-ultraviolet (UV) spectroscopy. The FIA technique was found to be effective in the resolution of ATR probe fouling in alkaline pulping liquors. Good spectral repeatability with a maximum relative standard deviation of the spectral intensity of less than 15% was obtained over a period of 5 days. Successful online monitoring of EA, sulfide, and dissolved lignin during laboratory pulping processes was demonstrated. The species concentrations measured by the ATR-UV sensor were found to be in excellent agreement with those obtained by traditional titration and conventional UV absorption measurements.