Colorimetry - Propagation of Errors and Uncertainty Calculations in Spectrophotometric Measurements treats the measurement of the colour of objects, based on the measurement of spectral irradiance (self-luminous objects) or that of spectral reflectance or transmittance (opaque or transparent objects), followed by colorimetric calculations according to the CIE system. Measurements are generally made in 5nm (or 10 nm) intervals in the spectral range of 360 to 780nm, and the 3 tristimulus values (X, Y and Z) are calculated from the 42-84 measurement points by standard equations. The statistical distribution of the measured R (lambda) values is probably normal; the correlation between the values varies depending on their position in the spectrum. The distribution of and the correlation between the X, Y and Z values are not known and they depend on the form of the spectral curve of each colour and on the operation of the measuring instrument. Complex formulae are used in the instrumental control of colours based on non-linear transformations of the X, Y and Z values into L*a*b*C*h°. The determination of the uncertainty of the results given in CIELAB coordinates or expressed in one of the colour difference formulae (delta)E*, (delta)ECMC or CIE(delta) E2000 is fundamental in the instrumental control of colours in any industry. Based on a large number of repeated measurements of different textile samples and ceramic standards, the distribution and other statistical characteristics of the directly measured R(lambda) values are analysed and - using the propagation of errors method - the uncertainties are calculated in colorimetric terms. The present research, a M. Sc. Dissertation work, was developed under the auspices of a co-operation agreement celebrated between the Post-graduate Programme in Metrology of PUC-Rio and SENAI/CETIQT, allowing for the inclusion of this M.Sc. Dissertation among the ten pilot projects which benefited from the financial support received from the FINEP/MCT Agreement number 22.01.0692.00, Reference 1974/01 (Fundo Verde-Amarelo). The project aims at driving the research effort in metrology to the solution of industrial problems, in this case the solution of a problem identified within the textile sector which requires to its solution advanced knowledge of colour metrology. Related the spectrophotometer measurements under the highest level of metrological control, the development and academic-scientific supervision of this M. Sc. Dissertation was performed at the laboratory facility of SENAI/CETIQT, an institution with proven technical and scientific competence in the field having sophisticated and well equipped laboratories in colour metrology meeting the measurement requirements needed to support the development of this research.