The aim of this study was to establish reference values for PImax and PEmax for the Mediterranean adult population. Male and female individuals between 18 and 83 years old meeting the criteria for consideration as references and residing in the metropolitan area of Valencia were assigned by decades to six subgroups, each containing at least 20 men and 20 women. PEmax was obtained from the point of maximum expiration (residual volume) and PImax was the point of maximum inspiration (total lung capacity). The cohort, which finally included 264 subjects (129 men and 135 women), was separated a priori by sex for data analysis. The following types of variables were studied: sociological (employment, educational level and exercise), biometric (age, height and weight) and spirometric results. A linear correlation analysis was performed for each pair of variables and a Kolmogorov-Smirnov test of normality was performed. In order to check the accuracy of PImax and PEmax readings, intra-individual variability was determined by performing three consecutive procedures over 3 days in 39 randomly selected individuals (18 men and 21 women). Significant inter-day and inter-test effects for respiratory pressures were thus ruled out. Predictive equations were worked out using a simple linear model including all predictive variables and eliminating weaker variables in a stepwise manner. Mathematical goodness of fit was assessed by a coefficient for multiple determinations (R2); also determined were the estimated standard error and statistical significance. We also compared observed and estimated values and the behavior of residual values in terms of their independence, normality and homoscedasticity. Reference limits were established by defining percentiles. The equations finally arrived at for men were as follows: PImax (-cmH2O) - 1.03 x Age + 0.59 x Weight + 133.07, PEmax (cmH2O) - 1.31 x Age + 263.12. The equations for women were PImax (-cmH2O) - 0.64 x Age + 125.18, PEmax (cmH2O) - 0.57 x Age + 0.65 x Weight + 116.26. Agreement with the usual references (the Black and Hyatt equations) was analyzed.