Aim: The goal of this study was to investigate the relationship between gastrointestinal complaints (dyspepsia, irritable bowel syndrome) and hematological parameters among recurrent aphthous stomatitis (RAS) patients. Material and Method: Forty-four RAS patients with a diagnosis of recurrent oral ulcers in oral mucosa were included in this study. They answered a questionnaire concerning oral aphthous properties, dyspepsia problems, and irritable bowel syndrome. Routine hematological screening and hemoglobin, vitamin B12, folic acid, and TSH were analyzed retrospectively. Data analyses were performed using SPSS. Results: Constipation complaints by females were statistically more frequent than those of males (59.3% vs. 11.8%; p< 0.05). There was a positive, statistically moderate and significant correlation between the time passed without having an aphtha (r= 0.343; p= 0.026) and lymphocyte level (r= 0.383; p= 0.028). However, there was no association between the time passed without having an aphtha and age (r= 0.112; p= 0.473), aphtha recurrence frequency (r= 0.05; p= 0.738), vitamin B12 (r= 0.019; p= 0.929), and Hb levels (r= 0.047; p= 0.781). Discussion: It was determined that there was positive correlation between aphtha size and lymphocyte level. Further studies should be designed in light of the association of RAS and gastrointestinal system disease.