Despite of their applicability betweennness constraints have (to the author’s knowledge) hardly been considered from the random structures point of view. They are essentially different from classical constraints like satisfiability, graph colouring ,...in that the underlying domain for each variable is unbounded and assignments presenting possible solutions are total orderings of the variables. Based on an experimentally observed threshold phenomenon concerning the satisfiability of random betweenness instances it is an obvious question to prove relevant results. Here obtain new lower bounds on the the size of random satisfiable instances.