There is only limited opportunity to measure the chlorine isotope composition of lunar material. Samples exist of lunar meteorites, that have the risk that they are contaminated with terrestrial material, and of Apollo return samples. Both sample types are only available in small quantities, making it necessary that chemical and isotopic analyses are done with utmost care on as little as possible sample material. For that reason, it is seen that many chlorine isotope studies on lunar material are applied by SIMS on lunar apatite (both meteorites and return samples). A smaller number of studies have been done by IRMS on larger (bulk) samples. An important difference exist between the two types of analyses and for that reason it still is important that, in spite of the relatively large amount of sample necessary per measurement, that bulk samples are measured. Because terrestrial samples are still mostly measured by IRMS techniques the measurement of lunar bulk samples by IRMS is important to facilitate proper comparisons between samples from Earth and the Moon.