DeriNet is a lexical network which models derivational relations in the lexicon of Czech. Nodes of the network correspond to Czech lexemes (i.e. single lemmas, possibly with only a subset of their senses), edges represent derivational relations between a derived word and its base word. The present version, DeriNet 1.2, contains 1,003,590 lexemes (sampled from the MorfFlex dictionary) with 1,001,394 unique lemmas, connected by 740,750 derivational links. Both rather technical and linguistic changes were made as compared to the previous version of the data; e.g. new version of the MorfFlex dictionary was used, derived words that contain a consonant and/or vowel alternation (e.g. boží) were connected with their base word (bůh).