I review geographical distribution, levels of infection and intraspecific morphological variation of Polystoma andinum Combes and Laurent, 1978 from the anuran host Melanophryniscus rubriventris. Also, I provide further information on the breeding biology of the host. The geographical distribution of P. andinum is extended further to the north and south of the original record coinciding with the major part of the range of its host. Parasite infection was recorded at seven of the eight host populations surveyed. Prevalence of infection in each population ranged from 9 to 33% and intensity from 1 to 14 parasites/host. Two morphological characters, reticulate intestine and haptor size:body length ratio, which show intraspecific consistency, readily distinguish P. andinum from each of the four species so far described in Argentina. All specimens assigned to P. andinum showed relatively wide intraspecific variation in hamulus shape. Nevertheless, morphometric analysis of five hamulus characters did not show major distinction between populations. Interlocality variability observed in this study highlights the importance of examining host samples from several localities. Reproduction of M. rubriventris in small shallow ponds is characterised by temporal and spatial uncertainty due to climatic conditions where eggs and tadpoles are exposed to high risks of mortality by pond desiccation. P. andinum reproductive effort may be concentrated into short periods following seasonal heavy rains when toads enter ponds to breed.