In the present study, time trends of the main quality indices in the pool of the Italian Network of Cancer Registries (pool AIRT) are presented for the period 1986-1997. The percentage of cases with morphological verification increased from 75% to 83% among males and from 77% to 85% among females. Cases known only from death certificates (DCO) decreased over time in both sexes; in recent years they were about 3% of the whole case-series. Mortality incidence ratio decreased over time, from 66% to 54% among males and from 55% to 48% among females. Also cases with unknown primary site showed a decreasing time tendency. Such quality indices are also presented for specific cancer sites and for elderly subjects (75+ years). The overall trends of quality indices showed an improvement in both the activity of Cancer Registries and of the Health System.