Spatial variations of chlorophylls and carotenoids in the gulf of Montijo were  examined during November of 1998. Six stations were sampled at one inshore  offshore transect extending from Puerto Mutis to Cébaco. Samples were taken at  each station for chlorophylls a, b and carotenoids analysis. Both temperature and  salinity increased from inshore stations to offshore stations. The salinity at  Gobernadora station was 28.2 ppt whereas in Puerto Mutis was 0.1 ppt. Piñas and  Puerto Mutis showed lower Secchi depths whereas high values were found at  Cébaco. The mean values of chlorophylls a, b, total chlorophyll and carotenoids  were 8.75, 17.25, 25.99 and 3.23 mg/mt3 respectively. The highest values were  found up-estuary and this spatial pattern was opposite to the temperature, salinity and  Secchi depth patterns. Chlorophyll b concentrations were higher than chlorophyll a  and the magnitude of the differences were higher up-stream than those down stream.