For almost three decades, California's criminal justice system has devoted increasing resources towards the arrest, prosecution, and imprisonment of drug offenders. Over the last two decades, simple marijuana possession has been the only offense category showing an increase, with marijuana possession arrest rates increasing by 127 percent. The result is that nearly one-fourth of all drug arrests in California are now for simple marijuana possession. This report to the California State Legislature on the current status of marijuana arrests shows, across various factors (trends, age breakdowns, racial breakdowns, and local arrest rates), an erratic and inexplicable pattern of county-based marijuana possession enforcement. In many major counties, arrests surge and plummet by 40 percent or more from year to year. In other instances, counties with similar demographics have arrest rates that may vary by 10-fold or more. It appears that the odds of getting arrested for marijuana are a function of geography, race, age, year, and local practices. It is recommended that to avoid more discriminatory and erratic enforcement of enforcement, the current push for legalization in the State should be seen as an opportunity for comprehensive review of the State's flawed drug criminalization and regulation policies. Tables, figures, references, and appendix