Resumen
The paper examines the corporate social responsibility (CSR) reporting practice at the frontier markets by using a comparative review of sustainability reporting practice according to the GRI framework. The research covers 31 companies included in the BELEXline and MBI10 indices in the period 2014-2018. The values of Social, Environmental, Economic and aggregate Sustainability Index, calculated using content analysis, indicate a low level of sustainability reporting practice. This is a consequence of a passive ownership and modest stakeholder pressures to the companies at two frontier markets and the lack of normative pressure on sustainability reporting. The grouping of the companies into clusters in accordance with the disclosure of sustainability indicators indicates significant inter- and intra-countries variations in practice. The reporting on sustainability issues differs among the companies according to their size, ownership structure, exchange market and industrial sector affiliation, which is on par with the developed capital markets.