Beginning with the withdrawal of the Ottoman occupation, the region known as Macedonia was divided among two or more European states. The entire region was never included in a single political unit. In 1990 Macedonia included all of the Yugoslav republic of Macedonia, the Pirin region of southwest Bulgaria, the part of northern Greece bordering the Aegean Sea and including Thessaloniki, and a very small part of eastern Albania. The Macedonian language, in which no written documents are known to have existed before 1790, had three main dialects. One dialect was closest to Serbian, one most resembled Bulgarian, and a third, more distinctive group became the basis for the official language.

The region's location in the middle of the Balkans and its lack of defined ethnic character made the dispute over the existence and location of a separate Macedonian nationality and control over its territory one of the most intractable Balkan issues of the late nineteenth and twentieth centuries. In general Bulgaria and Greece asserted that the Macedonians within their jurisdiction were ethnically indistinguishable from the majority population. Yugoslavia saw the Macedonians of all jurisdictions as a distinct ethnic group. But, beginning with independence in 1878, Bulgarians also claimed various segments of non-Bulgarian territory based on the ethnic Slavic commonality of the Bulgarians and the Macedonians. Residual claims on Macedonian territory were a primary reason for Bulgaria's decision to side with Germany during both world wars. In the division of territory after World War I, most of Macedonia became part of the Kingdom of the Serbs, Croats, and Slovenes (later the Kingdom of Yugoslavia), and was renamed "South Serbia." After World War II, Yugoslavia strengthened its hold by making Macedonia a separate republic and recognizing the Macedonians as a distinct nationality (see World War I and Foreign Policy in the Late 1930s , ch. 1).

The Bulgarian position maintained that leading patriots such as Gotse Delchev and Iane Sandanski (who had fought for Macedonian independence from the Turks) and cultural figures such as the Miladinov brothers (who promoted education and the Slavic vernacular during the National Revival period) were products of Bulgarian culture and considered themselves Bulgarians, not Macedonians. In 1990 many people in the Pirin region identified themselves as Bulgarian, but some opposition Macedonian organizations such as Ilinden (named after the 1903 IlindenPreobrazhensko uprising for Macedonian independence on St. Elijah's Day) sought recognition by the Bulgarian government as a minority separate from the Bulgarians. This position was based on the assertion that Macedonians were a separate nationality with a distinct language and history.

No reliable data showed how many people in Bulgaria, or in all of Macedonia, considered themselves Macedonian or spoke a Macedonian dialect in 1990. Those who considered the Slavs in Macedonia as Bulgarians c455 cited statistics for the whole region at the time it was first divided after World War I. At that time, 1,239,903 Bulgarians, or 59 percent of the population, were listed. The Bulgarians were a majority in both Yugoslav (Vardar) Macedonia (759,468 people) and in Bulgarian (Pirin) Macedonia (226,700 people). Later Bulgarian censuses, however, showed sharply varying numbers of Macedonians according to what political agenda was to be supported by a given census. The 1946 census, for example, identified over 250,000 Macedonians, reportedly to back President Georgi Dimitrov's short-lived plan for federation with Yugoslavia. Then, between the censuses of 1956 and 1965, the number of Macedonians dropped from 187,789 to 9,632. After that time, the Bulgarian census ceased identifying citizens by nationality.

Data as of June 1992