Citizens of other EU member states and Australia, Canada, Israel, Japan, New Zealand and the USA can stay in Bulgaria visa-free for up to 90 days. Citizens of other countries should check the current requirements with their nearest Bulgarian embassy or consulate before their departure. Visas cannot be obtained at border crossings.
At the time of writing, visitors wishing to extend their visit to Bulgaria beyond the 90-day limit have to apply for a residence permit at the Immigration Office (02-982 3764; bul Maria Luisa 48; 9am-5pm Mon-Fri). This is likely to be a time-consuming, bureaucratic nightmare, and nobody here will speak anything but Bulgarian. It’s probably far better to contact the Bulgarian Embassy in your own country for advice before you travel if you envisage being in the country for more than three months. The situation, especially for EU citizens, may well change over coming years.