To attain 100% completion in The Lost and Damned, the player must accomplish all of the following:
- Complete 23 storyline missions (Clean and Serene to Get Lost).
- Complete 25 Gang War side missions.
- Complete 12 Bike Race side missions.
- Finish Importing/Exporting Bikes for Angus-10.
- Terminate 50 seagulls.
- Find two Random Characters.
- Complete Stubbs' jobs-5.
- Win a game of arm wrestling, pool, darts, and air hockey against anyone.
- Bring Terry or Clay to friendship activities (air hockey, darts, drinking, eating, pool, show, and strip club) at least once.