The MMWR Summary of Notifiable Diseases, United States, 2001 contains, in tabular and graphic form, the official statistics for the reported occurrence of nationally notifiable diseases in the United States for 2001. These statistics are collected and compiled from reports sent by state health departments to the National Notifiable Diseases Surveillance System (NNDSS), which is operated by CDC in collaboration with the Council of State and Territorial Epidemiologists (CSTE).