The main purpose of this chapter is to collect together in a logical sequence all measurements of beams formed both by single capillary tubes in Section 11.2 and by plane capillary arrays in Section 11.3 and to compare these with the theoretical evaluation presented in Section 9.2. These two groups are further divided into comparison of theory with experiment in turn for the throughput, the axial intensity and the angular distribution of the beam, which we use to obtain the halfwidth if this is not stated specically. This covers the majority of measurements, but in Section 11.4 we treat focussing arrays separately from plane arrays. Section 11.5 discusses cases where only an indirect comparison of theory with experiment is possible. Unfortunately some results are not presented before reduction of the data from our preferred quantities, but we include them in appropriate sections when it has been possible to make comparison with the equations given in Chapter 9. In Section 11.6, conclusions are drawn from the previous sections and nally in Section 11.7 we make what comparison is possible with beams produced by free jet sources. The aim in all cases is to establish primarily the reliability of the application of the equations given in Section 9.2 but also the range of their validity as well as to look critically at measurements.