SummaryFour crocodile populations have been examined by aerial photography with a view to assessing their length frequency distributions.The assumptions, and the limitations attached to such assumptions, necessary to convert length frequency information into information on the age structure, and hence the status, of the population are considered.Environmental conditions of value in understanding the status of the populations are listed.The Victoria Nile population is considered to show adequate recruitment, but dispersal of young crocodiles tends to give the converse impression. The population is probably stable and has not been heavily exploited in the past.The Grumeti River population may represent a local aggregation mostly of large males from Lake Victoria, probably retreating from human induced pressures. There is little recruitment through breeding, and the largest crocodile encountered in this study are members of this population.The Lake Rudolf population is a typical healthy population with high recruitment and high juvenile mortality. The population is probably stable, but may be expected to decline as fishing interests on the west shore expand. Growth is retarded in the Rudolf population.The Lorian swamp population is expanding rapidly probably after a period of heavy mortality wrought by hunters shooting for skins. The present conflicts with human/livestock interests is expected to increase, resulting in stabilization and decline of crocodile in the swamp.Some comments are made on the possible influence of various environmental parameters on present status and trends of the populations.