Can you hook up a connection to your 1999 es300 Lexus radio for your mp-3 player?

yes there are many ways. if you have a tape player you can just buy the tape adapter that plugs into any headphone jack ex. mp3, portable CD player etc. you can also buy a FM transmitter they run from about $10-$45 depending on features that you want they plug directly into the headphone jack of your mp3 and you just turn your radio to the station that the FM transmitter is set to and you have mp3s in your car. there are also adapters for factory radiOS that can add mp3 integration. if you want an aftermarket radio, there are plenty of options for mp3 playing. the cheapest and easiest is the FM or casette adapter.

crutchfield has a very good selection of all of the above mentioned options here is the link to their mp3 page just copy and paste the address

http://www.crutchfield.com/m_770/iPod-MP3-Car-Adapters.HTML?tp=15