The quality of humidity measurements from different radiosonde sensors was studied using satellite data. Sensors vary in accuracy, with Vaisala sensors performing the best. Russian sensors tend to have a wet bias in the upper troposphere and a dry bias in the middle troposphere. Chinese, Indian, Russian, and U.S. sensors have high random errors in the upper troposphere, making them less reliable for studying humidity changes. It is important to use data from a single sensor type for long-term trend studies to avoid biases between sensors.