An electrochemical sensor for organic molecules such as ethylene includes an electrochemical cell, gas sample inlet means and means for detecting current produced by the oxidation of the organic molecule at the anode of the cell. The sensor is capable of sensing multiple organic molecules in some embodiments. A voltage is applied to the anode of the cell to provide energy to drive the oxidation reaction and produce a corresponding current. The sensor of the invention can be made as a small, hand-held unit that is capable of real-time detection of various organic species.