This bulletin summarizes the availability of immigrant numbers during December 2010. Consular officers are required to report to the Department of State documentarily qualified applicants for numerically limited visas; the Bureau of Citizenship and Immigration Services in the Department of Homeland Security reports applicants for adjustment of status.  Allocations were made, to the extent possible under the numerical limitations, for the demand received by November 10 2010 in the chronological order of the reported priority dates. If the demand could not be satisfied within the statutory or regulatory limits, the category or foreign state in which demand was excessive was deemed oversubscribed.  The cut-off date for an oversubscribed category is the priority date of the first applicant who could not be reached within the numerical limits. Only applicants who have a priority date earlier than the cut-off date may be allotted a number.  Immediately that it becomes necessary during the monthly allocation process to retrogress a cut-off date, supplemental requests for numbers will be honored only if the priority date falls within the new cut-off date which has been announced in this bulletin.

http://www.travel.state.gov/visa/bulletin/bulletin_5197.html