travel Lisbon to Seville

Flying is usually the best option. You should be able to find inexpensive flights on the discount airlines.

'all routes go to Madrid first before Seville' - not correct for bus, as Lisbon to Seville can be direct overnight - www.alsa.es A quick look at flights with Vueling gives the €90 mark, one way, for end August. 'I've read that to rent a car in Portugal and drive it in to Spain is very costly.' - I would not have thought so. (To hire a car in one country and drop off in another will certainly be costly.) Find quotes, ensure the hirer is aware of your intent.

As Neil said, the expense comes when you pick up a rental car in one country and return it in another. If you return it in the same country you picked it up (even a different city in that country, and even if you've driven it into other countries before your return to the country of pickup), there's usually no surcharge; of course, you have to check with the rental company. To find flights, on both budget carriers (like Vueling) and "legacy" carriers (like TAP Air Portugal), use http://www.skyscanner.com. Yes, in general, connections between Spain and Portugal are poor (certainly not what we US-ers, thinking of them as practically one country, expect them to be). If flying won't work for you, check the bus website Neil posted.

This may or may not make sense - it depends on how long you are going to be there in each country and where specifically you want to travel, but you can rent a car in one country, drop that off in a town close to the border, make your way acres the border (by bus or taxi), then rent another car in the next town and drive onward. I've done this for Portugal and Spain and it saved what would have been a huge drop-off fee (600 Euro). It involved some hassles (bus, ferry, another bus, and a bit of walking across 3 towns) it ate up half a day, but it saved a good chunk of money and was a bit of an adventure.

Thank you for your input. When I checked on Vueling flights, I got a $400 plus fare for one-way. Might just stay in Portugal, but that would be very disappointing.

Hi Carol, We are going to go to Spain, and Portugal too (in July), and after a lot of time to research, and I have found a reasonable route: from Lisbon, fly to Barcelona, and from Barcelona to Seville. If you have the time, you can add Barcelona to your itinerary, and you will find the flights are right. Goof luck.

Disappointingly, Barcelona is not an option for this trip, as we have to spend three days in Estoril, Portugal. I have just located a NY Times blog that is interesting:
http://intransit.blogs.nytimes.com/2009/03/24/getting-from-seville-spain-to-lisbon-without-wasting-time-or-money/ David Allan, the writer, suggests that the 6-7-hour bus trip from Seville to Lisbon is the best solution. We could fly from Lisbon to Madrid and backtrack, but the trip would extend at least three weeks. I find that we start getting tired after two weeks.

I found the same to be true regarding the high drop-off fee for car rental from one country to the next.
So what we did (albeit in the opposite direction) back in 2007, was take the bus from Seville (nice, cheap, fast) to Faro, and rented a car there, then drove to Lisbon and dropped the car off there. Of course, we stopped at points in between (Evora, etc), and stretched the travel over several days. If you timed it right, it would take less than 8 to 10 hours, but not much...