The present paper addresses the subject of the variability of stress assignment in Erzya. The aim of the analysis reported here was establishing speaker-, utterance- and word-related data that might account for the alternation of the initial and non-initial stress patterns. The material used for the analysis contained spontaneously produced utterances recorded by 33 speakers of Erzya originating from different areas of the Mordvin Republic and diaspora. The overall distribution of the stress patterns in the data of spontaneous speech proved to be more variable than it has been observed in script reading. The occurrences of initial stress exceeded those of non-initial stress; however, non-initial stress was used more often than in reading. The analysis revealed differentiation in the distribution of the patterns of stress in the idiolect-related data. The tendency towards the assignment of initial stress was more salient in the data of the idiolects characterized by the reduction of vowels in non-initial syllables. There was less difference between initial and non-initial stress occurrences in the data of the idiolects which use only full-formation vowels. In the dialects that use reduced vowels, reduction might have been the consequence of the diminishing mobility of stress. The assignment of stress, as the test material showed, could not be conditioned by the type of word structure. It is rather the functional role of the word in an utterance that might be associated with the mobility of stress. The recurrent responses of the speakers recorded in a dialogue were found to contribute to the increase of non-initial stress occurrences.