Abstract: The object of the present invention is to provide a method for producing aggregates of autologous fibroblasts for producing autologous fibroblasts having been aggregating in a fibrous state, and an aggregate produced by this method. Another object is to provide a composition for repairing a defect in a skin or gingival soft tissue which can keep favorable treatment effect by remaining in the treated area over a long period of time, and an injection having this composition. The above-mentioned problems are solved by a method of producing an aggregate of autologous fibroblasts which comprises the step of culturing autologous fibroblasts in a culture medium with vitamin C added and the step of culturing autologous fibroblasts by a culture method selected from among rotary culture, shaking culture and slant culture so as to form a fibrous aggregate by an extracellular matrix containing collagen secreted by the autologous fibroblasts, the aggregate produced in this way, and so on.