Background: Deep x-ray lithography using synchrotron radiation is a prominent technique in the fabrication of high aspect ratio microstructures. The minimum lateral dimensions producible are limited by the primary dose distribution and secondary effects (Fresnel diffraction, secondary electrons scattering, etc.) during exposure. Aim: The influence of secondary radiation effects on the fabrication of high aspect ratio microstructures with submicrometer lateral dimension by deep x-ray lithography is characterized. Approach: The microstructures under investigation are one-dimensional gratings. The influence of secondary effects on structural dimension is simulated and compared to the experimental results. The quality criteria and possible defects arising in experiments highlight the importance of the mechanical stability of the photoresist. Results: From the simulation results, the minimum period of microstructures that can be produced is about 600 nm. Experimentally, microstructures with 1.2 μm minimum period (resist width of ∼700 nm) and height of ∼10 μm could be fabricated. Conclusions: Simulation results show the feasibility for fabricating gratings with a period less than 1 μm. ... mehrTo achieve these values also in experiment, it is necessary to increase the mechanical stability of the high aspect lamellae. The outcome of these results allows one to reduce the expensive and lengthy product development cycle.