The verbal class which is characterized by a suffix -nu- in the infinitive and -ne- in the present shows considerable dialectal diversity in Croatian and in the other western South Slavic languages. In many dialects, verbs belonging to this class have a suffix -ni- in the infinitive, aorist, participles and/or present. The aim of this paper is to explain how these dialectal forms and the relevant dialectal isoglosses have arisen. It argues that the allomorph -ni- < *-ny- was originally found in the infinitive, while -nu- < *-nǫ- used to be restricted to the aorist.Druga glagolska vrsta, za koju su karakteristični sufiksi -nu- u infinitivu i -ne u prezentu, pokazuje znatnu dijalektalnu raznolikost u hrvatskom jeziku i u drugim zapadnojužnoslavenskim jezicima. U mnogim govorima glagoli koji pripadaju ovoj vrsti imaju sufiks -ni- u infinitivu, aoristu, participima i(li) prezentu. Cilj je ovog rada objasniti kako su nastali dijalektalni oblici i relevantne dijalektalne izoglose. Pokazuje se da je alomorf -ni- < *-ny- izvorno bio ograničen na infinitiv, dok je -nu- < *-nǫ- bio ograničen na aorist