Bucharest to Sofia??

I used google. There is a bus connection maybe with change in Ruse. It takes over 6 hours. There is one bus daily to Ruse and 4 from Ruse to Sofia according to google. I was not able to find schedule. But that's usual in eastern European countries. There are many companies and I suspect that there could be even direct bus and maybe more than one a day. So I would wait until I would get to Bucharest or at least to Romania and then go to travel agency and start from there. In eastern Europe little improvisation is needed and you cannot book everything from the States or where you are.

Thank you for this information. I had determined that there WAS bus transport but couldn't figure out how to do it or where it would arrive in Sofia so I can be picked up by a transfer service. I believe it will be very late at night.
You've been helpful in suggesting working it out once I'm in Bucharest.
Sandy

Last year there was also train transportation between the two cities, with perhaps a bus leg somewhere along the way. I would check with the local tourist organization in Bucharest, or perhaps even in another Romanian city you plan to visit earlier. Those folks were very helpful to me. Some English will be spoken.

I found the online info about domestic bus schedules generally reliable (don't remember the website(s)--found by Googling), but that international trip was trickier. I remember seeing some instructions online about taking the bus to the town on the Romanian side of the border, then taxiing to Ruse to pick up a Bulgarian bus. Perhaps the instructions were in a post on the ThornTree forum. In any case, Google will probably find it. After I purchased my through-ticket on the train I read that Ruse is picturesque, but I didn't get to see it.

Many Romanian buses have a quirk that I found very annoying for foreign visitors: You often must make a reservation in advance, but you can't do that at the bus station, nor can you simply buy a ticket ahead of time. The reservation must be made by telephone. I had no phone service in Romania, so I threw myself on the mercy of locals, and they were kind enough to call for me.

One thing you'll discover is that the public buses and trains in both Romania and Bulgaria cover about 30 miles per hour. Fascinating countries, though.

The direct train runs daily at this time:

Sa, 17.09.16

Bucuresti Nord Gara A dep 12:50, Train 461, Subject to compulsory reservation

Sofia arr 22:20

Duration: 9:30; runs daily

Border crossing: Russe(FR) .