The first L. Valerius Flaccus, an associate of Cato the Elder, was curule aedile in 201 BC, praetor in Sicily in 199, and consul with Cato in 195. Flaccus defeated the Boii and Insubrians during his consulship, then in 191 was legate at Thermopylae. As triumvir in 190, he helped defend Placentia and Cremona, and founded Bononia. He became a censor along with Cato in 184, and princeps senatus when Scipio Africanus Major died, himself dying in 180. Politically, Flaccus was a conservative, and joined Cato in the role of defending Roman tradition again Hellenism.
Persons named "L. Valerius Flaccus" are listed as consul in 152 BC and 131 BC.
Another L. Valerius Flaccus was consul in 100 BC along with Gaius Marius; Rutilius Rufus characterized Flaccus as "more slave than colleague" however. As censor in 97, he noted for helping enrol more Italians as citizens. He was made princeps senatus in 86, and worked with for agreement with Sulla, eventually joining his party and securing Sulla's election as dictator, for which Flaccus was rewarded with the post of magister equitum. Flaccus does not appear further, and is presumed to have died soon after.
Another L. Valerius Flaccus was aedile in 98 BC, but prosecuted (unsuccessfully) afterwards by Decianus. Flaccus was then praetor, then governor of Asia. He was a suffect consul in 86, taking command against Mithridates, passing a law cancelling three-quarters of all debts, and leaving for Asia. He was murdered in a mutiny by Fimbria.
The previous Flaccus' son was also L. Valerius Flaccus (d. 54 BC). He served in Asia under his father, but fled to his uncle Gaius, who was in Gaul. He later served as military tribune in Cilicia, quaestor in Spain under Piso, a legate of Metellus in Crete. As urban praetor he was with Cicero in the Conspiracy of Catiline, and then governor in Asia. In 59 Cicero defended him in a speech. Flaccus was then a legate of a later Piso, in Macedonia.