In cold regions, ground freezing and thawing is repeated several times duing winter. Ground freezing and thawing causes damage in two ways : the first is due to the frost heaving itself, whereas the second arises from decrease of the strength of the soil during the spring thaw. It follows that unconfined compressive characteristics of foamed mixture lightweight soils may also be greatly affected by freezing and thawing. Although many studies on engineering properties of foamed mixture lightweight soils have recently been made, studies on the effects of freezing and thawing on unconfined compressive characteristics of foamed mixture lightweight soil have not yet been investigated. For this reason, to investigate the effects of freezing and thawing on unconfined compressive characteristics of foamed mixture lightweight soil, unconfined compression tests were peformed on foam mixture lightweight soils subjected to freezing and thawing action. The unconfined compressive strength of foamed mixture lightweight soil gradually decreases with an increase in the number of freezing and thawing cycles although the first event has the greatest effect for soils. The unconfined compressive strength of foamed mixture lightweight soil subjected to freezing and thawing is about 0.7 times less than that of specimens without freezing and thawing. The decrease of unconfined compressive strength is caused by decrease of suction and destruction of soil structure due to freezing and thawing.