The effect of angle of inclination on the rise velocity of a single gas slug and overall liquid-phase mass transfer coefficient (K(L)A) have been measured for a CO2 bubble in a closed tube. Water and two aqueous solutions of glycerol were used. The results on K(L)A and the rise velocity U-b theta have been empirically correlated. A method has been proposed to estimate the interfacial area of the slug in an inclined position. Plausible explanations have been offered for the observed jump in the K(L)A for larger tubes (D > 0.0257 m) and longer (L/D > 3) slugs.