Study results indicate that when conducting delta13C, delta2H, and delta18O isotopic analysis of samples, the type of storage container used had little bearing on the results obtained because of the subsequent sample preparation protocol. More pronounced and significant differences were found, however, when analyzing the same samples for delta15N, although there was no consistent isotope shift from 6 weeks to 6 months. The findings suggest that the storage container of choice is a glass vial with a securely crimped lid. Paper, plastic eppendorff tubes, and plastic self-seal bags should be avoided because of the possible presence of additives and plasticizers, which could alter the isotopic signature of the samples. Samples of scalp hair and fingernails from the same subject were placed into each of the following types of packages: plastic self-seal bags, plastic eppendorff tubes, paper envelopes, pieces of tin foil, and crimp-sealed glass vials. The subject whose hair and nails were collected for this study had not traveled or changed his diet during the sampling interval. After completing the two storage periods, all samples were cleaned according to a published standard procedure. 2 figures and 17 references