Abstract In two of our previous reports [1–2], a general scheme for the crystallographic analysis of lath martensite in an Fe-Ni-Mn alloy has been developed. From all outward indications, it appears that the Fe-Ni-Mn martensite is typical of that found in carbon steels. The present investigation is thus aimed to see if the previous information transcends to the lath martensite formed in an Fe-0.2%C steel. The results indicate that (1) parallel laths of the same variant within a given region have the same orientation and habit plane (and correspond to a “packet”) as before; (2) large packets of martensite frequently contain other crystallographic variants, and at least three distinct variants have been identified; (3) no retained austenite between adjacent laths was found. The analyses of the Fe-Ni-Mn and Fe-C lath martensites are mutually consistent.