Continuous phase mass transfer coefficients have been measured for a stream of drops falling freely in a stagnant liquid. Drop streams were produced by a dripping method and by a jet breakup method. Water and isobutanol, mutually saturated, were used as the dispersed and the continuous phases, respectively. Sodium hydroxide was used as solute and was transferred from the bulk solution of isobutanol to water drops which was initially free of solute. Resistance to the mass transfer was observed to be on the continuous phase side. The mass transfer coefficient and terminal velocity of drop streams were measured experimentally. The experimental results show that the mass transfer coefficient in the drop stream is affected by the shielding effect of the previous drops. An approximate analysis was conducted for the shielding effect of a drop stream on mass transfer coefficient caused by the superposing wakes produced by each drop in the stream. The resulting equation describes the effect of interdrop distance on mass transfer coefficient in the continuous phase side and the experimental data have been correlated as K-t/U-t(0.5) versus interdrop distance l. Good results were achieved and also can be applied to other liquid-liquid systems.