Does higher commercial insertion constitutes for livestock keepers an opportunity in fostering the transformation of their farms, or a risk likely to further weaken their farms? This issue is arising in Northern Cameroon where traditional livestock farming systems are hampered by high pressure on land while high population growth and rapid urbanization stimulate the development of dairy products and beef markets. A research was carried out to identify the effects of commercial insertion on the sustainability of farms. The methodological approach adopted criss-crosses the study of breeding practices and the analysis of cattle marketing channels. Investigations and an annual follow-up were carried out at the level of the herds, farms, cattle markets, slaughter-house and consumers. The engagement of livestock keepers in trading is effective, but it operates in a careful way, farmers preferring risk minimization to income optimization. The adjustments related to commercial insertion range from a slight modification of breeding and especially of commercial practices and diversification of products to the change of farm structure. Income generated by engagement in the marketing channels are used to preserve livestock thus conserving capital, to increase livestock size, to modernize the breeding activity by purchasing more inputs, or to invest in extra-farm activities. The deficiency of support services, inadequate information, the organisation and functioning of the cattle marketing channel, the low decision-making capacity of farmers make commercial insertion a source of vulnerability. Principal concerns of farmers relate to the reduction of livestock size, poor economic results, hindering of breeding activities and disturbing of farm structure. The supply of technical and management advice will help farmers to better deal with internal factors of this vulnerability. The control of external factors requires collective actions, regulations and suitable policies to make th