Background: Many studies documented an association between a Helicobacter pylori infection and the development of human gastric cancer. None of these studies were able to identify Helicobacter pylori as a cause or as the cause of human gastric cancer. The basic relation between gastric cancer and Helicobacter pylori still remains uncertain. Objectives: This systematic review and re-analysis of Naomi Uemura et al. available long-term, prospective study of 1526 Japanese patients are performed so that some new and meaningful inference can be drawn. Materials and Methods: Data obtained by Naomi Uemura et al. who conducted a long-term, prospective study of 1526 Japanese patients with a mean follow up about 7.8 years and endoscopy at enrolment and in the following between one and three years after enrolment were reanalysed. Statistical Analysis Used: The method of the conditio sine qua non relationship was used to proof the hypothesis without a Helicobacter pylori infection no development of human gastric cancer. The mathematical formula of the causal relationship was used to proof the hypothesis, whether there is a cause effect relationship between a Helicobacter pylori infection and human gastric cancer. Significance was indicated by a p-value of less than 0.05. Results: Based on the data published by Uemura et al. we were able to make evidence that without a Helicobacter pylori infection no development of human gastric cancer. In other words, a Helicobacter pylori infection is a conditio sine qua non of human gastric cancer. In the same respect, the data of Uemura et al. provide significant evidence that a Helicobacter pylori infection is the cause of human gastric cancer. Conclusions: Without a Helicobacter pylori infection of human stomach no development of human gastric cancer. Helicobacter pylori is the cause of human gastric cancer (k = +0.07368483, p-value = 0.00399664).