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Very close encounters of stars might lead to significant perturbations oftheir Oort-type clouds, planetesimal belts and planetary systems. We havecalculated encounter parameters of Hipparcos stars using HIP2, Pulkovo andCRVAD2 catalogs of radial velocities. It turns out that some stars haveencounters within 0.1 pc from each other and might be on an essential collisioncourse up to few thousands AU. We present here examples with accurateastrometric data and stable with respect to errors of radial velocities within$\pm 0.3$ km/s. They include $\beta$ vs. $\gamma$ Virginis, 61 Cygni vs.$\chi^1$ Orionis as well as close encounters involving $\eta$ Bo\"otis, ABDoradus, 61 Urs{\ae} Majoris and others.

Nemesis encounters of nearby Hipparcos stars