Entrants in the California Science & Engineering Fair qualify through an affiliated county or regional fair. These fairs are held throughout the State during the months of February and March (and occasionally even late January or early April).
All affiliated fairs have been allocated a certain number of projects which they may qualify to CSEF, based upon judging done by fair judges (i.e. not special or recognition award judges external to the fair). In some fairs this number will correspond to "all first place winners" but in others it may include "all first, second, and third place awards" or only a fraction of the first place winners. Each affiliate has the final authority and responsibility for choosing the best project from its fair to represent itself. See the Eligibility Rules for further details.
Eligible winners at these affiliated county and regional fairs must then submit an Application to the California State Science & Engineering Fair.