This is the first SS level which was first reached during his battle with Frieza after Krillin's death. In this stage there eyes are blue, there hair is golden yellow and it sticks up in several large lumps. When they are powered up they have a golden yellow aura of flames around them one of the main signs of being a SS.
The advantages of this level is that they have much increased strength, speed, stamina and agility. There are no disadvantages of this level accept for the that you can't be as powerful as you could be in SS2 or over. You change to SS when you surpass your maximum power in your normal body and are usually under emotional stress or anger.