The effects of reducing the concentration of the potassium iodide (KI) cathode electrolyte from 1% to 0.5% in electrochemical concentration cell (ECC) ozonesondes flown at Lauder, New Zealand (45 ¿S, 170 ¿E) have been investigated. Four studies were made to assess these effects: 1% and 0.5% KI ozonesonde performance was compared directly in three dual flights, one year of 1% KI and one year of 0.5% KI ozonesonde profiles were compared with near-simultaneous lidar profiles, integrated ozonesonde profiles were compared with Dobson spectrophotometer measurements over the same period, and ascent and descent profiles were compared for both KI concentrations. Ozonesondes flown with a 1% KI solution showed positive differences of 3% to 8% in the ozone profile and ~5% in the ozone column compared with the 0.5% KI ozonesondes, which also showed better agreement in profiles and ozone column compared with the lidar and Dobson spectrophotometer measurements respectively. ¿ 1998 American Geophysical Union