The last comprehensive publications about the theory and practice of rhinomanometry appeared more than 20 years ago. Since the 1980's, the general progress of sensor techniques, fluid physics and data processing was accompanied by the permanent work of the authors to analyze the errors of rhinomanometry and to create a fundament for a contemporary and practical method that can be used in functional diagnostics of the nasal air stream. In this special document, the objectives and measurement principles, as well as the history of rhinomanometry are described in the first three chapters. It is pointed out, that the key parameters are not only intranasal pressure and flow, but also the factor time. The technical requirements as following from the dynamics of breathing are described. The process of averaging of rhinomanometric data lead to a separate and time-dependent analysis of the changes of pressure and flow and implicated the introduction of the 4 breathing phases (ascending and descending curve part in inspiration and expiration) into rhinomanometry and is therefore called 4-Phase-Rhinomanometry (4PR). Chapter 4 is containing a comprehensive analysis of the practical errors, which may follow neglecting the 4 breathing phases. The in chapter 5 described mathematical-physical concept of 4PR is based on the introduction of the terms "steady" and "unsteady" flow, in addition to the up to now used terms of laminarity and turbulence. After the derivation of the HOFFRICHTER-equation as explaining the loops around the intersection point of the x-axis and y-axis, a clinical classification of the rhinomanometric findings is given and confirmed by physical experiments with "artificial noses". Finally, testing the rhinomanometric method by CFD (Computational Fluid Dynamics), lead to the same conclusions as to the importance of 4 phases of the breathing cycle. The precondition for the worldwide introduction of new parameters into the 4PR is a comprehensive statistical analysis. The disadvantages of the present recommended standard values are described in chapter 6. Following previous studies in 5800 cases, the parameters Vertex Resistance (VR), Effective Resistance (Reff) and their logarithmic transformations have been investigated in 1580 rhinograms of different degrees of obstructions, also including the correlations to a VAS. It could be confirmed, that the parameters VR and Reff after logarithmic transformation, have a significant and high correlation to the sensation of obstruction. The new clinical classification of obstruction and conductance of the nose is proposed in Table 1 for Caucasian noses. Table 1. Clinical classification of obstruction and conductance for Causcasian noses. [see text for table]. Chapter 7 is dedicated to the advantages of 4PR in the functional diagnosis of nasal valve problems. Graphical as well as numerical solutions are available by the fact, that the motions of the nasal entrance as caused by the breathing process are now visible from the shape of the 4PR-curve. Discussing practical aspects in chapter 8, the start point of proposals and discussions are the standard recommendations of the ISOANA and the results of its consensus conference in 2003. In particular the calibration processes, hygiene, the correct attachment of the pressure tube at the nostril ("tape method") and the different measurement procedures (AAR, APR), decongestion and provocation tests are extensively described. Both the final chapters are clinical contributions from mainland China, which are of high importance because of the racial differences in nasal respiratory function. In chapter 9, tests of the assessment of normal nasal airway in adult Chinese by 4PR, rhinomanometry and acoustic rhinometry are presented. This investigation lead to the conclusion that 4PR is an important supplement to classic rhinomanometry and acoustic rhinometry, if the classification of obstruction is adapted to the higher basic resistance of the Chinese population. Chapter 10 is dealing with 4PR and acoustic rhinometry in the functional evaluation of septal deviations and concludes, that both methods are valuable objective instruments for the evaluation of nasal obstruction.