This paper describes an experimental investigation to determine the dynamic loads produced by groups of up to 64 people jumping in time to a musical beat. It focuses on the changes in the characteristics of the load with increasing numbers of people.The recorded responses were analysed to determine peak accelerations and displacements. The data were also processed to find the first three Fourier components of the load and these were used to derive the attenuation of Fourier coefficients with group sizes. A similar form of relationship for the fourth Fourier coefficient was determined. The load model was then used to calculate the floor response for comparison with the measurements. The measurements demonstrate that both safety and serviceability must be considered in the design of floors to withstand this type of loading. 12 pages.