It is possible to write a word whose body consists of arbitrary assembly code. The assembly receives parameters and returns values as per the platform's ABI; marshalling and unmarshalling Factor values is taken care of by the C library interface, as with alien-invoke.

Assembler opcodes are defined in CPU-specific vocabularies:

•	cpu.arm.assembler
•	cpu.ppc.assembler
•	cpu.x86.assembler

The combinator for generating arbitrary assembly by calling a quotation at compile time:

alien-assembly ( args... return parameters abi quot -- return... )