Time of harvest during crop ripening was accompanied by large differences in lint percentage of cotton in the Ord River Valley. Lint percentage generally rose at least 3 per cent from first to last harvest. Varieties showed a wide range in lint percentage. Varietal values remained very stable between seasons in a three year trial but in two out of three seasons there was a pronounced time of sowing effect, lint percentage rising with sowing from November to at least February. Significant variety x time of sowing interactions were recorded. In three trials nitrogen fertilizer reduced lint percentage, though there was no consistent relationship between rate of nitrogen application and lint percentage decrease. Spacing, phosphorus, potash, and defoliation had no direct effect on lint percentage.