Two new cave-dwelling ground beetle species, Trechus gamae sp. n. and Trechus lunai sp. n., from Portugal, are described. The new species are included in the Trechus fulvus-group by their morphological characters. The work provides diagnostic characters in particular those of the structure of male genitalia, and the distribution of the hypogean species of the fulvus-group at the Estremenho Karstic Massif is mapped. Some comments on the seasonal activity of T gamae sp. n. are also given. An identification key to the males of the T. fulvus-group species from the Estremenho Karstic Massif is presented, and biogeographical comments are also included.