A method of cleaning fouled process equipment which includes a process vessel (10) fouled by an organic foulant, includes spraying a hydrocarbon stream at a pressure of at least 69 bar(g) at fouled surfaces inside the process vessel (10) thereby to dislodge the organic foulant from the fouled surfaces. The hydrocarbon stream is sprayed from at least one nozzle (24) located inside the process vessel (10). The hydrocarbon stream is at a temperature below the melting point of the organic foulant or below the melting point of a major component of the organic foulant when the organic foulant is a multi-component organic foulant. The dislodged foulant is removed from the process vessel (10).