The aim of the investigation was to assess the allergizing properties of a new nanocolloidal preparation based on aluminum gamma-oxide labeled by technetium-99m for scintigraphic and intraoperative detection of sentinel lymphatic nodes in experiment.Materials and Methods. A series of experiments was performed on 80 guinea pigs, 30 Balb/c mice, 40 CBA/CaLac mice and 70 outbred mice of both genders. To study allergenicity various doses of preparation were administered subcutaneously, intramuscularly, intravenously, intradermally as a single injection or by a course. Allergizing properties of the radiopharmaceutical were investigated according to the "Guidelines on the assessment of allergizing properties of drugs".Results. Administration of Nanocolloid, Tc-Al 2 o 3 radiopharmaceutical did not result in the intensification of anaphylaxis systemic reaction in the animals of the examined groups relative to the control. A single injection did not cause inflammatory reaction to Concanavalin A in the examined animals. When guinea pigs were immunized by the preparation, no delayed allergic reaction was revealed. Studying sensitizing effect of the preparation by 20 skin applications no redness or edema of the skin at the site of application was observed.Conclusion. Nanocolloid, 99mTc-Al 2 o 3 radiopharmaceutical in the studied doses and under the selected experimental conditions does not possess allergizing properties.