Other participants were delegates from various national Social-Democratic parties: three each from the Social-Democrats of Poland and Lithuania, the Bund and the Lettish Social Democratic Labour Party, one each from the Ukrainian Social-Democratic Labour Party and the Finnish Labour Party, and also a representative of the Social Democratic Labour Party of Bulgaria.
Partisipan lainnya adalah delegasi dari berbagai partai Demokrat Sosial nasional: tiga masing-masing dari Demokrat Sosial Polandia dan Lithuania, Badan Buruh Yahudi Umum dan Partai Buruh Demokrat Sosial Latvia, satu masing-masing dari Partai Buruh Demokrat Sosial Ukraina dan Partai Buruh Finlandia, dan juga seorang perwakilan dari Partai Buruh Demokrat Sosial Bulgaria.