We have developed a method to calculate the fundamental parameters of the vertical structure of the Galaxy in the solar neighborhood from trigonometric parallaxes alone. The method takes into account Lutz-Kelker-type biases in a self-consistent way and has been applied to a sample of O-B5 stars obtained from the Hipparcos catalog. We find that the Sun is located 24.2 +/- 1.7 (random) +/- 0.4 (systematic) pc above the galactic plane and that the disk O-B5 stellar population is distributed with a

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... scale height of 34.2 +/- 0.8 (random) +/- 2.5 (systematic) pc and an integrated surface density of (1.62 +/- 0.04 (random) +/- 0.14 (systematic)) 10^-3 stars pc^-2. A halo component is also detected in the distribution and constitutes at least 5 O-B5 population. The O-B5 stellar population within 100 pc of the Sun has an anomalous spatial distribution, with a less-than-average number density. This local disturbance is probably associated with the expansion of Gould's belt.