Personal safety equipment is necessary for using any power equipment. In addition to standard gear, there is specialized safety equipment for use with a chainsaw:
Leg protection such as chaps or cut-resistant pants
A hard hat for protection when cutting and trimming overhead
Gloves with enhanced gripping surfaces and cut resistance
Eye protection with side shields
Hearing protection such as earplugs or earmuffs
Boots or shoes with steel toes and nonskid soles
For more information on using a chainsaw safely, see Chainsaw Safety. Making sure a chainsaw is in good working order is also a part of chainsaw safety. How to Use and Maintain a Chainsaw provides information on sharpening the chain and other practices to keep a saw running properly.