Sam Bird led the way in an eventful Formula Renault 3.5 free practice session around the streets of Monaco.
The Briton, who took pole position in the Principality in GP2 last year, had a couple of stints at the top of the times as the session went into its closing stages.
On both occasions ISR driver Bird deposed Alexander Rossi from top spot, and the Arden Caterham driver was unable to respond after he crashed at Casino Square towards the end of the session.
A late effort from Marco Sorenson dropped Rossi to third, and the American was far from the only driver to hit trouble as the field tried to make the most of its only track time before qualifying on Saturday morning.
Sorenson's Lotus team-mate Richie Stanaway kicked things off with an early crash after clattering the kerbs at the Swimming Pool, while Lucas Foresti caused the first red flag when he spun at Rascasse and caused a traffic jam.
At the same time his DAMS team-mate Arthur Pic went off at Sainte Devote. The Frenchman had managed to keep his car out of the barriers, but he could not prevent it from stalling as he tried to rejoin the track.
Ferrari junior driver Jules Bianchi was in the wars again when his car developed a small fire with 20 minutes to go, and the Tech 1 driver had to complete a whole lap with a smoking car as it started just as he passed the pit entrance.
Carlos Huertas and Giovanni Venturini also hit trouble in the closing stages, and the session concluded under a red flag with Bird on top.
Despite his crash Rossi ended up third behind Sorenson. Kevin Korjus was fourth for Tech 1, ahead of a trio of rookies in Kevin Magnussen (Carlin), Nico Muller (Draco), and championship leader Robin Frijns (Fortec).
Red Bull-backed Lewis Williamson's tough start to the season continued, as the Scot's track time was halted when his Arden car got stuck in gear.
Pos Driver Team Time Gap 1. Sam Bird ISR 1m25.046s 2. Marco Sorensen Lotus 1m25.243s + 0.197s 3. Alexander Rossi Arden 1m25.299s + 0.253s 4. Kevin Korjus Tech 1 1m25.601s + 0.555s 5. Kevin Magnussen Carlin 1m25.626s + 0.580s 6. Nico Müller Draco 1m26.099s + 1.053s 7. Robin Frijns Fortec 1m26.528s + 1.482s 8. Andre Negrao Draco 1m26.833s + 1.787s 9. Daniil Move P1 1m26.962s + 1.916s 10. Nick Yelloly Comtec 1m27.003s + 1.957s 11. Zoel Amberg Pons 1m27.086s + 2.040s 12. Mikhail Aleshin RFR 1m27.231s + 2.185s 13. Lucas Foresti DAMS 1m27.736s + 2.690s 14. Anton Nebylitskiy RFR 1m27.844s + 2.798s 15. Walter Grubmuller P1 1m28.177s + 3.131s 16. Vittorio Ghirelli Comtec 1m28.447s + 3.401s 17. Will Stevens Carlin 1m28.484s + 3.438s 18. Carlos Huertas Fortec 1m28.494s + 3.448s 19. Nikolay Martsenko BVM Target 1m28.813s + 3.767s 20. Jake Rosenzweig ISR 1m28.856s + 3.810s 21. Giovanni Venturini BVM Target 1m29.031s + 3.985s 22. Yann Cunha Pons 1m29.272s + 4.226s 23. Jules Bianchi Tech 1 1m29.407s + 4.361s 24. Lewis Williamson Arden 1m30.416s + 5.370s 25. Arthur Pic DAMS 1m40.412s + 15.366s 26. Richie Stanaway Lotus 1m48.995s + 23.949s