The Budapest Stock Exchange's main BUX index lost 1.83% to 19,371.17 at noon on Monday.
The index opened down 2.79% in the morning in line with global trends after the United States sovereign rating was downgraded by Standard & Poor's at the weekend.
OTP Bank fell 1.86% to HUF 4,603, oil and gas company MOL dropped 1.91% to HUF 17,950, drug maker Richter lost 1.63% to HUF 35,500 and Magyar Telekom was down 1.71% at HUF 517.
Share turnover amounted to HUF 13.3 billion for the morning.
Major Western European share indices were all down, with London's FTSE losing 1.79%, Frankfurt's DAX falling 2.39% and the CAC-40 in Paris dropping 1.79%.
Elsewhere in the CEE region, Warsaw's WIG-20 lost 0.78% and Prague's PX-50 fell 2.98%.