Using satellite data only, a unique model of the upper-ocean mixed-layer has been developed recently by Yan for calculating the thermal inertia (or the heat flux change per unit temperature change per day) of the mixed-layer from which daily mean mixed-layer depth is estimated. Thus digital maps of the oceanic daily mixed-layer depth in the vicinity of the Sargasso Sea for 14 May-30 August, 1982 have been generated from visible, near-infrared, thermal-infrared and microwave observations made by radiometers on board the NOAA-7, -8, GOES and Nimbus-7 satellites. The errors incurred in producing such maps are of two general type: measurement from satellites and model simplification. The sensitivity of the modelled mixed-layer depth to simplifications in the model (modelling errors) and to errors in data used for forcing the model (data errors) is considered here. To emph isize the oceanographic relevance of these errors, we express the errors in mixed-layer depth as a function of model errors and data errors, and compare these errors with the daily mixed-layer depth changes of in situ data. We also discuss some of the error sources in this paper. Thus the applications and practical limitations of the model are evaluated. The results of this study show that errors in the surface temperature field cause the largest errors in the predicted mixed-layer depth, because the surface temperature errors affect both the heat flux estimation and the thermal inertia estimation. The errors in wind speed field are less severe although these errors may become more significant at wind speed higher than 8.5 ms−1, below which most of our field comparisons were made. The smallest uncertainty is found to occur with remotely estimated changes in sea-surface albedo as this error in a very small way affects the heat flux. These results imply that the errors due to direct atmospheric radiative effects or those which determine radiative fluxes and the determination of sea surface temperature should be reduced to improve prediction of mixed-layer thermal inertia and mixed-layer depth in summer using satellite data.