Due to de high number of stray dogs and cats which defecate in public places in Mexico City (3 millions approximately), in addition to domestic dogs and cats, exists the potential risk to man of infection by Toxocara sp. eggs. A study to determine the contamination frequency by Toxocara sp. eggs in public parks, public flower beds, and home gardens in Mexico City, Distrito Federal, was carried out in the 1995 first semester. Fourteen hundred and five soil samples were collected from 156 public parks, 83 public flower beds and 42 home gardens across the 16 delegations in Mexico City, Distrito Federal. Samples were processed by the zinc sulfate centrifugal flotation method, and supernatants read by microscopy. Out of the whole 281 sampled sites, 12.5% were found contaminated with Toxocara sp. eggs. Positivity found was: 10.9% in public parks, 13.3% in public flower beds and 16.7% in home gardens. Ninety percent of the eggs were embryonated or larvaeted measuring 60 to 90 micrometers. The high contamination frequencies found make necessary to prompt for Public Health measures granted the risk of infection acquisition spread on the most exposed population (children) provided that it is acquired via geophagia.