Grounded outlets

[John]

I don't have grounded outlets, but I need to plug in a three prong plug. Can I just replace the 2 prong outlet with a 3 prong outlet?

[Kevin]

No, you cannot simply replace your old 2-prong outlets with 3-prong outlets. This is dangerous and a violation of the National Electrical Code (NEC).

3-prong outlets which do not have appropriate ground don't serve there intended safety function and mislead people into believing the outlets are grounded.

Short of rewiring with appropriate grounding wires, an acceptable option is to replace the ungrounded outlets with GFCI (Ground Fault Circuit Interrupter) outlets and label them with the available stickers indicating "Ungrounded Outlet".