These data files were acquired during the course of the 3rd FrenchBIC MetBio summer school taking place in and around Marseille. The data were acquired during the “stopped flow” practicals. The data correspond to the reaction of Myoglobin with various concentrations of azide, triggered using a stopped-flow apparatus and followed by UV/Visible spectroscopy. The concentrations of azide can be deduced from the names of the files and are expressed in millimolar. The concentrations of myoglobin are variable but always much lower than that of azide. The purpose of this dataset is to be used as training data for analysing multiwavelength kinetic data. It will be the subject of a data analysis tutorial using the free software QSoas, to be published there. With the exception of the WTV-Azide-0.5mm_3.txt, all the files are in a “matrix” format, in which the first column gives the time and each column after the first corresponds to the absorbances over time of a single wavelength. The WTV-Azide-0.5mm_3.txt uses a different format, in which each line corresponds to a wavelength time absorbance triplet. Useful background reading: Coletta et al, 1996, DOI: 10.1111/j.1432-1033.1996.00049.x De Sanctis et al, 2007, DOI: 10.1529/biophysj.106.098764