Results of the last researches testify to close interrelation between rising of the I-FABP level and a damage rate of a small bowel of both inflammatory, and ischemic character. Now there is an accumulation of clinical data which will allow to develop concrete clinical references according to changes of I-FABP in a blood of patients with various pathology of a small intestine. Aim. Research objective determination of the I-FABP level in control group of patients without intestine diseases, and in groups of patients with functional diseases of an intestine. Material and methods. 83 patients who were on hospitalization aged from 23 till 83 years (middle age of 58,5±15,7 years) of 55 (66%) women and 28 (34%) men were examined. Among the examined patients at 16 (19%) patients the diagnosis of IBS with constipations, at 16 (19%) IBS with a diarrhea, at 31 (37%) the patient transferred a colectomy was established (17 patients of left-side, 14 patients right-side). Control group at 20 (25%) patients with erosive gastritis, it is also not revealed given clinical and laboratory research of a lesion of an intestine. Results. At examination groups of patients were registered by us broad fluctuations of an indicator of I-FABP from 34,5 to 444,9 pg/mL. The highest rates, both on average, and on a median became perceptible at patients with a left-side gemicolektomy, and IBS from diarrheas. Patients with a left-side gemicolectomy had them authentically above, than at patients with a right-side gemicolectomy (r=0,05), IBS with a constipation (r=0,004) and at erosive gastritis (r=0,003). The lowest indicators of I-FABP in a blood became perceptible at patients with erosive gastritis, they made 64,9±38,7 pg/mL, at a median of 53,3 pg/mL, the highest I-FABP level in this group of patients made 191,8 pg/mL. Considering that at these patients it didn’t become perceptible neither a clinical, nor tool symptom of a lesion of a small intestine we consider that this indicator can be used as version of the normal maintenance of I-FABP in a blood which makes from 47,2 to 82,5 pg/mL. Conclusion. Definition of I-FABP in a blood is a perspective method of diagnosis of diseases of a small intense, it is possible to take values from 69,0 to 172,7 pg/mL for normal value of this indicator.