In 2004, 38,972 malaria cases and 106,704 suspected cases with 31 deaths were reported by the annual case reporting system in 1,005 counties of 23 Provinces/Municipality/Autonomous Region (P/ M/A) and the annual incidence was 0.38/10 000, a decrease of 4.2% than that of the last year, which is the year that the disease was slightly rolled back after consecutively increased since 2001. As an important development of the case reporting system, the internet reporting system started in 2004, majority of the malaria cases (38 254) were reported through internet from 1,074 counties of all the 30 P/M/A except Qinghai Province. Among the 1,005 counties with reported malaria cases, 32 counties were with an incidence of more than 10/10,000 distributing in Yunnan (19 counties), Hainan (10) and Anhui (3). There were 61 counties in which the malaria incidence was between 1/10,000 and 10/10,000. The number of Plasmodium falciparum malaria cases was 4,891, accounting for 12.6% of the total cases, of which 35.0% (1,714) were imported cases reported in 174 counties/cities of 18 P/M/A. Indigenous falciparum malaria was found in 45 counties/ cities of Yunnan and Hainan Provinces, of which 29 counties/cities were in Yunnan, decreased by 35, 16 were in Hainan, increased by 2 compared to that of 2003. Yunnan and Hainan Provinces are still the relatively high transmission areas. Yunnan has ranked No. 1 in the country in terms of the number of cases while Hainan ranked No. 1 by malaria incidence in recent years. 22 247 malaria cases were reported from the two provinces in 2004, accounting for 57.1% of the total reported cases in the country. There were 12,865 cases with 25 deaths reported from Yunnan, and the incidence was 3.09/10,000, a decrease of 16.6% than that in the last year. Among the reported cases, 3,251 were falciparum malaria, decreased by 7.9% in comparison to 2003. The number of reported cases in Hainan was 9 832, with an incidence of 11.64/10 000, 46.6% increase than the last year. In central China, the re-emergence of malaria was considerable in provinces along the Huai River, especially in Anhui Province. The case number in Anhui has been the second or third largest in the country since 2001. 8909 malaria cases and 14,542 suspected cases were reported from the Province in 2004, accounting for 22.9% of the total cases in the country, with an incidence of 1. 38/10,000 increased by 9.8% than that in 2003. Hubei reported 2,714 malaria cases with an incidence of 0.47/10,000, decreased by 60.8%. The number of reported cases in Henan was 2,211, decreased by 43.1%. 676 cases were reported from Jiangsu, almost the same as that in 2003. Focal outbreaks occurred in 109 villages of 13 counties in Anhui, Hubei and Jiangsu, where Anopheles sinensis is the principal transmission vector. Malaria cases reported from the above 4 provinces accounted for 37.2% of the national figure. Cases reported from Guizhou, Sichuan, Guangxi, Guangdong, Zhejiang, Shanghai and Hunan in southeast China occupied about 5% of the total cases, over 50% of which were imported cases. Less than 100 cases were reported from each of Fujian, Chongqing, Shandong, Jiangxi, Liaoning, Shaanxi, Shanxi, Gansu, Xinjiang and Heilongjiang Provinces in the year. In summary, although malaria cases slightly decreased after several years' consecutive increase, malaria is still an important problem of public health in China, especially in the southern and central parts. Yunnan and Hainan still face a critical situation of malaria endemics with the spread of P.falciparum, especially in the 25 border counties in Yunnan. In central parts of the country, especially in Anhui, malaria prevalence was highly unstable with frequent focal outbreaks in areas along the Huai River, which reveals new challenges to the national malaria control program.