The annual pattern of burial depth in natural populations of the infaunal bivalves Tagelus dombeii (Tellinacea) and Venus antiqua (Veneracea) is described in relation to annual food availability in both the water column and the sediment and abiotic factors (temperature and salinity) at Coihuín tidal flat, in southern Chile. A field experiment in which burial depth was measured in situ each month (over 14 months), with the aid of a fixed-length nylon thread attached to the shell. For T. dombeii the results showed a significant increase in burial depth with increasing bivalve size and syphon weight. Tagelus dombeii had a mean burial depth of 17·5 cm, which was three times more than in V. antiqua (5·30 cm). The burial depth dynamics for both species displayed a strong correlation with food availability in the water column. Approximately 60% of the variability in burial depth in T. dombeii and V. antiqua was explained by concentration of chlorophyll-a in the water column. Food concentration on the sediment surface did not effect burial depth, i.e. deposit feeding seems to be of minor significance in either species.