PRETRIAL RELEASE DATA FOR THE COUNTY ARE ANALYZED, INCLUDING STATISTICS ON EACH MAJOR RELEASE MECHANISM: STATION CITE (RELEASE AFTER BOOKING AND UPON PROMISE OF REAPPEARANCE, LIMITED TO MISDEMEANANTS AND TO PERSONS FOR WHOM POLICE HAVE NO WARRANT); BAIL; AND OWN RECOGNIZANCE (OR). THE FREQUENCY WITH WHICH EACH MECHANISM IS USED AND THE LENGTH OF DETENTION ASSOCIATED WITH EACH MECHANISM ARE CONSIDERED. THE IMPACT OF AN EXPANDED PRETRIAL SERVICES PROJECT ON THE DEMAND FOR JAIL SPACE IS ASSESSED, WITH EMPHASIS ON THE PROJECT'S EFFORTS TO INCREASE THE NUMBER OF DETAINEES RECEIVING OR INTERVIEWS. THE ASSESSMENT INDICATES THAT THE PROJECT HAS NOT REDUCED THE SIZE OF THE DETAINEE POPULATION. FORECASTS OF THE AVERAGE UNSENTENCED CUSTODY POPULATON FOR ALAMEDA COUNTY IN 1990 AND 2000 ARE DEVELOPED, TOGETHER WITH ESTIMATES OF OVERCROWDING FREQUENCY AND MAGNITUDE FOR VARIOUS JAIL CAPACITIES. IT IS CONCLUDED THAT, NO MATTER WHAT REASONABLE JAIL CAPACITY IS CHOSEN, THERE WILL BE SOME OVERCROWDING ON SOME DAYS, AND THAT A CONTINGENCY PLAN FOR HANDLING TEMPORARY OVERCROWDING SHOULD BE DEVELOPED. APPROACHES TO SUCH CONTINGENCY PLANNING ARE SUGGESTED, AND FIVE OPTIONS FOR BUILDING FACILITIES TO MEET PROJECTED PRETRIAL DETENTION NEEDS ARE OUTLINED. DETAILS OF FORECASTING METHODOLOGY AND SUPPORTING DATA ARE APPENDED. (LKM)