Biological and chemical-physical data were obtained from burrows of the red swamp crawfish, Procambarus clarki, and the adjacent ponds and ditch during the burrowing period. Burrows constructed by mature and immature crawfish were of the same general pattern. Burrows usually consisted of an undulating downward channel, varying in depth, devoid of a connection with the adjacent pond or ditch. The tunnel was covered by a chimney or mud plug at the top and was enlarged at its deepest part into a chamber. Variance in the diameter of the channel seemed correlated with the total bodylength of the inhabiting crawfish. Fauna present in burrow water consisted mainly of planktonic crustaceans. In general, the animal groups in burrows were similar to those present in the adjacent pond or ditch but fewer species and numbers occurred in the burrows. The benthic fauna in the burrows was dominated by oligochaetes whereas aquatic insect larvae, mainly diptera, dominated in the ponds and ditch. Air, water, and soil temperatures fluctuated during the observation period but were closely related in the burrows and the adjacent pond or ditch. The turbidity was very high in the burrows and exceeded that of the ponds and ditch at all times. No apparent seasonal trend in the chemical water properties could be established. Very low oxygen, high free carbon dioxide and slightly acid water characterized the burrow habitat. Chemical soil properties in burrows and in the adjacent ponds or ditch were similar.