Kalven and Zeisel estimated that in 1955, 53,380 criminal jury trials took place in State courts. According to the 1978 State Court Caseload Statistics, estimates of the number of criminal jury trials in many States were still not available. Although data on criminal jury trials in Federal courts for 1955 and 1980 are available, it is impossible to extrapolate this data to State courts due to statistical constraints and the significant difference in the type of cases heard by State and Federal courts. Estimates of the number of jury trials were computed according to types of cases heard: (1) limited jurisdiction courts which normally hear nonfelonies, (2) general jurisdiction courts which normally hear felony cases in States that have limited jurisdiction courts, and (3) general jurisdiction courts which hear both felonies and nonfelonies in States that do not have limited jurisdiction courts. Separate estimates were computed on the basis of the point at which the State defined a jury trial (at verdict or before), type of offense, unit of count (defendants, indictments, information or charge), and the number of trials or dispositions. According to this method, there were at least 64,490 reported State court criminal juries in 1978, a figure which can serve as a benchmark for computing future changes in the number of jury trials. Extensive tabular data and 10 footnotes are provided.