Shipboard (~7 m) ozone measurements made in the equatorial Pacific Ocean between 20 ¿N and 17 ¿S and 140¿--160¿ W confirm the existence of a distinct ozone minimum in the vicinity of the equator in the late spring, its decline in the summer and its absence in autumn. This minimum could not be correlated with high biological activity in surface waters. Coincident aircraft measurements of ozone from near sea surface (50--100 m) to 2 km in altitude were made along 150 ¿W at stations at 10 ¿N, 0¿, 5¿ and 12 ¿S in May--June 1984. Aircraft data identified the existence of a distinct ozone maximum between the lifting condensation level (LCL) or cloud base (Zb) and the trade wind inversion, with ozone mixing ratios amounting to 2--2.5 times the ozone levels in the well-mixed subcloud layer. A gradient of decreasing ozone with decreasing altitude extended from the LCL (or Zb) to the near-surface superadiabatic region but did not include it.