The most famous work of Plutarch includes biographies in pairs of a Greek and a Roman in each volume. Most biographies include a comparison of the personalities of the subjects.

Plutarch's purpose was not so much to present the historical details of each subject's life, but to study their characters and psychology.

The Parallel Lives are an important source of information about great personalities. For some of the subjects, Plutarch provides details that are not found in other sources.

The pairs of subjects are:

• Solon - Publicola
• Themistocles - Camillus
• Theseus - Romulus
• Lycurgus - Numa Pompilius
• Pericles - Fabius Maximus
• Gaius Marcius - Alcibiades
• Aristides - Cato the Elder
• Pelopidas - Marcellus
• Agis, Cleomenes - Tiberius, Gaius Gracchus
• Aemilius Paullus - Timoleon
• Dion - Brutus
• Cimon - Lucullus
• Pyrrhus - Gaius Marius
• PhiloPimen - Titus Flamininus
• Nicias - Crassus
• Phocion - Cato the Younger
• Alexander - Julius Caesar
• Demosthenes - Cicero
• Lysander - Sulla
• Agis - Pompey
• Eumenes - Sertorius
• Demetrius - Marcus Antonius
• Aratus - Artaxerxes
• Galba - Otho