The use of medicinal plants is an increasing phenomenon among the majority of people in many developing countries. Some of the harvested medicinal plants are often stored for shorter or longer periods prior to usage. Evidence from recent studies has demonstrated the pharmacological efficacy of short and long-term stored plant materials when compared to freshly-harvested ones. In an attempt to evaluate the effect of long-term storage on the safety of some commonly used medicinal plants, the Ames test which involved the use of three Salmonella typhimurium tester strains (TA98, TA100 and TA1535) were conducted. Current findings indicate the absence of any mutagenic effects resulting from the storage of medicinal plant materials for as long as 16years. Although freshly collected Acokanthera oppositifolia extract demonstrated a mutagenic effect against TA1535 strain at the highest concentration tested, no such effect was observed in the stored material. Further studies involving metabolic activation systems and in vivo conditions may further elucidate the effect of long-term storage on the safety of medicinal plants.