When the news broke last Tuesday that five Columbia University students were arrested for selling drugs—including cocaine, ecstasy, and LSD—to undercover cops, the campus was stunned. Known as “Operation Ivy League,” the sting revealed what students at the prestigious university already knew: When campus enforcement and student activity create a “permissive environment” for recreational drug use, students are wont to take advantage.

Two and half years ago, a drug raid at San Diego State University culminated in the arrest of 75 students. Last September, two University of North Carolina students were arrested in a raid that resulted in the seizure of 321.6 grams of cocaine. And earlier this year, a Reed College student died from a heroin overdose, prompting the college’s president to issue a promise to curtail drug use on campus.

Gallery: Ranking The 50 Druggiest Colleges

Campus drug use has been on the rise for decades, as nearly half of full-time college students binge drink or abuse drugs at least once a month, according to a 2007 study by the national Center on Addiction and Substance Abuse on drugs in American colleges. The percentage of students that smoke marijuana or use other illegal drugs, such as cocaine or heroin, doubled from 1993 to 2005.

The Daily Beast combed available statistics to figure out which campuses have both environments that may be permissive of drug use as well as a student body that partakes in illegal drug use. To rank the colleges and universities, we first turned to College Prowler, the largest student review database, to see which institutions had “drug scene” grades, which illustrate how students rate the prevalence of drugs on campus. A high grade, i.e. an A+, indicates that drugs and alcohol are not noticeable on campus and there is no pressure to use drugs. College Prowler provided an initial list of nearly 400 colleges and universities across the country of all sizes and academic rigor.

We then considered the surrounding environment, using the most recent data on illicit drug, marijuana, and cocaine use by state for 18-25 year olds, according to the U.S. Department of Health and Human Services 2009 National Survey on Drug Abuse. Lastly, we referred to U.S. Department of Education data for the number of on-campus arrests for 2009 for drug-law violations for each school. An arrests-per-capita metric was calculated for each school based on the Department of Education’s student population tabulations.

The College Prowler grades were assigned a numerical value according to the letter grade assigned, which was weighted one-third of each school’s final score; the arrests-per-capita rank and drug use ranks were also ranked one-third of the final rank.

Correction: An earlier version of this story incorporated incorrect statistics in one category for Northeastern University, Washington and Lee University and Old Dominion University, respectively. This version has the correct rankings.