Garrigue and Remy described a system for higher-order polymorphism that forms the basis of the support for polymorphic methods in OCaml. This can be used for higher-rank polymorphism, but the result is not convenient. However, the same underlying ideas can be used to directly support polymorphic parameters. We describe these underlying ideas and give typing rules for polymorphic parameters. Based on these rules, we’ve implemented polymorphic parameters in our branch of OCaml and have been using them in production for almost a year.