The use of a multiagent system (MAS) to model and simulate biochemical reactions is useful for several reasons. Four of them are, first, it is possible to represent directly each molecular type using a specific agent type, second, it is possible to duplicate the agent types in differents quantities to retrieve the real molecular concentrations, third, it is possible to make the agent reacting with each other under certain conditions or events in order to represent the reactions between the real molecules and fourth, the agents take place in a 2D or 3D environment where many situations and phenomena can be simulated. In this paper we detail different stages allowing the creation of a MAS representing one or more biochemical reactions occurring concurrently in a same environment.