The proper relaxation time necessary before reading deep sea reversing thermometers depends on the time constants of the main and auxiliary thermometers. In a computer simulation, the maximum error is corrected water temperatures is centered at a lagtime equal to the average of the time constants, while the magnitude of the error is proportional to the difference in time constants. For the thermometers we tested, a maximum error of 0.03 ¿C was incurred by prematurely reading deep sea reversing thermometers.