Efavirenz is a non-nucleoside reverse transcriptase inhibitor clinically used for the treatment of patients with human immunodeficiency virus (HIV) as it is effective in reducing viral load in HIV-positive patients. The objective of the present study was to investigate cosolvents and surfactants effect on efavirenz under basic conditions. The breakdown of efavirenz in basic aqueous solution of cosolvents and surfactants at 60°C ±0.2 was studied. The breakdown was determined by UV spectrophotometry. The drug was seen to follow the apparent first order rate kinetics and rate constant for the degradation were obtained from plot of logarithm percent drug remaining versus time. The kinetic reaction was shown to be hydroxide ion catalysed. A significant increase in the stability of efavirenz was noted with the cosolvents and surfactants investigated. The results obtained from the study suggested that cosolvents and surfactants could be used to formulate and stabilise liquid pharmaceutical dosage forms of efavirenz under basic conditions.