A 19-year-old man was airlifted to hospital with a suspected broken arm after falling while walking on snow and ice-covered Snowdon wearing a pair of trainers.
Rescuers said training shoes were unsuitable given conditions on the mountain.
The teenager was in a party of walkers when the incident happened on Sunday.
He was winched from the Pyg Track path into a rescue helicopter and flown to hospital at Bangor at 15:00 GMT.
Last week, Llanberis Mountain Rescue Team rescued a 19-year-old man wearing plimsolls, jeans and a leather jacket and suffering from hypothermia while walking on Snowdon.