In October 2005, reports indicating a possible association between Guillain-Barré Syndrome (GBS) and receipt of meningococcal conjugate vaccine (MCV4) (Menactra, Sanofi Pasteur, Inc., Swiftwater, Pennsylvania) were made to the Vaccine Adverse Event Reporting System (VAERS). GBS is a serious neurologic disorder involving inflammatory demyelination of the peripheral nerves. During March 2005-February 2006, eight confirmed cases had occurred within 6 weeks (i.e., the time window of elevated risk noted for GBS after administration of other vaccines) after MCV4 vaccination. This report summarizes nine additional GBS cases reported to VAERS during March-September 2006. This report also provides a preliminary analysis of data from VAERS and the Vaccine Safety Datalink (VSD) since MCV4 became available in the United States in March 2005 and includes all 17 cases of GBS reported since June 2005. Although these data suggest a small increased risk for GBS after MCV4 vaccination, the inherent limitations of VAERS and the uncertainty regarding background incidence rates for GBS require that these findings be viewed with caution. Because of the risk for meningococcal disease and the associated morbidity and mortality, CDC continues to recommend routine vaccination with MCV4 for adolescents, college freshmen living in dormitories, and other populations at increased risk.