Measurements of the most important parameter of the blanket of a thermonuclear reactor—tritium production—are necessary for testing present nuclear data and analytical methods. A cylindrical model containing lithium metal was designed and constructed. The tritium production was measured by three methods: (a) tritium determination by a liquid scintillation method, (b) internal gas counting of the tritium β-activity, and (c) recording of the α-particles associated with the tritium producing reactions by solid-state track detectors. The space-dependent tritium production rates were calculated using discrete ordinates and Monte Carlo methods. The agreement between liquid scintillation and Monte Carlo results is as good as can be expected taking into account the uncertainty of the nuclear data used for the calculations.