In central Italy, in 1997 and 1998, in order to determine the optimum harvest period, the quantity and quality of oil during fruit ripening (from beginning of November to mid-December) was monitored in the olive cultivar Frantoio, Leccino and Maurino. In all the cultivars the olive oil content increased during the considered time, with a higher intensity in November. Maurino had higher fruit oil content (% d.w.) and lower cake content than Frantoio and Leccino. Leccino had the quickest and most intense pigmentation followed by Maurino and, finally, by Frantoio. In all cultivars, fruit drop was quite low in November, then it increased up to values of 10-16% in December. In all cultivars, the oil free acidity and peroxide number were optimal during the entire experiment. The oil fatty acid composition did not change significantly. The oil polyphenol content, always rather high, was less in mid-December. The oil obtained from olives harvested in November was more fruity, bitter and spicy than that obtained from olives harvested in December. The maximum amount of oil on the tree was found at end-November. Therefore, considering that at this stage oil quality is also at a very good level, the results indicate that the second half of November is the best time for harvesting. Drupe characteristics (i.e. pigmentation, oil content, detachment force) and fruit-drop, can be used as harvest indexes, therefore the values reported for these parameters in correspondence to the optimal harvesting time can be used as references.