| undercover agent | 23.70 | He was an undercover Secret Service agent. | ||
| undercover officer | 13.10 | They are undercover officers. | ||
| undercover operation | 6.85 | At first, Wolff conducted undercover operations. | ||
| undercover police | 4.81 | Were they undercover police? | ||
| undercover investigation | 3.55 | The two groups conducted a six-month undercover investigation. | ||
| undercover work | 3.16 | Undercover work also has its dangers. | ||
| undercover troop | 2.83 | Undercover troops mingle with, arrest protesters. | ||
| undercover detective | 2.70 | Undercover detectives greet doctors. | ||
| undercover cop | 2.57 | A female undercover cop. | ||
| undercover unit | 2.17 | APTV has a special feature on the undercover unit. | ||
| undercover narcotic | 1.78 | Undercover narcotics work was her calling. | ||
| undercover investigator | 1.65 | Undercover investigators exposed the scam. | ||
| undercover policeman | 1.58 | They were undercover policemen. | ||
| undercover drug | 1.38 | The caller, it turned out, was an undercover federal drug agent. | ||
| undercover sting | 1.38 | Nine Texas men were indicted in the undercover sting. | ||
| undercover operative | 1.32 | We are undercover operatives on a top-secret assignment. | ||
| undercover soldier | 1.18 | The undercover soldiers of the S-A-S have been singled out for their bravery in the Gulf War. | ||
| undercover security | 0.99 | In addition, undercover security men worked as ushers, leading other patrons to their seats. | ||
| undercover informant | 0.79 | He had sold two sawed-off shotguns to an undercover informant. | ||
| undercover surveillance | 0.79 | Undercover surveillance began last month. |