In 2002, the internet based reporting system OSIRIS was introduced in the Netherlands and by the end of that year had fully replaced the paper-based reporting system. The objectives of OSIRIS were to improve timeliness and completeness of surveillance data on infectious diseases reported from regional to national level. We compared the timeliness of infectious diseases reported by the conventional paper-based system in 2001 with those reported by OSIRIS in 2003. Two distinct types of delay were compared: (1) total delay: defined as time between symptom onset and reporting at national level and (2) central delay: defined as time between regional and national reporting. Median delays between both systems were compared using the Wilcoxon Rank Sum-Test. We also compared electronic reports received via OSIRIS in 2003 to those received through the conventional system for 2001 for completeness of specific data fields. The Fisher exact test and the Mantel-Haenzel test with Yates correction were used to determine the significance of proportions of completed data fields in each system. Results showed the median central delay was significantly reduced for all diseases in OSIRIS compared to conventional reporting system. Overall, the median central delay was reduced from 10 days (interquartile range 4) in 2001 to 1 day (interquartile range 1) in 2003. Except for cases of malaria, the total delay, from symptom onset to national reporting, was also significantly reduced. In addition, OSIRIS records contained more complete information than conventional records. In total, in 2003, 92.3% of data field examined were complete compared with 81.3% in 2001. This study documents the benefits of electronic reporting of infectious disease surveillance data in terms of improved timeliness and completeness.