1. Experiments have been conducted concerning the blassom-end-rot in tomato plants in relation to the varietal susceptibility, the nitrogenous fertilizers and the fruit-thinning. 2. Among nineteen varieties, Fukujiu-2, Ponderosa, Sparks Earliana, Kurihara, June Pink were sccffered from severer attacks of the blassom-end-rot than the others. 3. Bearing fruits equal degree, varieties having long stems seemed to be suffered from the disease more severely than the others hauing short ones. But, when fruiting was specially wrong, there could be found little of the disease regardless of the length of the stems. 4. According to the increase of nitrogen supply, fruits were suffered more severely from the disease and the plants hauing long stems looked weak. 5. When only two fruits were allowed to set on one cluster by practicing the fruit-thinning, the fruits were suffered from the disease less than when many fruits on one cluster without thinning.