Because of inconsistencies in literature data, the crystal structure of ZrTe3was redetermined from single-crystal data and the electronic band structure was calculated using density functional theory in the local density approximation (LDA) and the linear muffin tin orbital method (LMTO). ZrTe3crystallizes in the monoclinic space groupP21/mwitha=589.8(1) pm,b=392.69(3) pm,c=1010.3(1) pm, andβ=97.81(1)° (Z=2) in the ZrSe3structure type (ωdata collection,Rw=1.88%). In the layer structure of ZrTe3almost linear homonuclear Te chains in [100] direction with alternating distances of 279.4(1) and 310.5(1) pm are observed. In addition to these, there are several other Te–Te distances below the sum of the radii of Te2−ions (370–380 pm). From the band structure calculations we found these homonuclear contacts to be responsible for the unexpected metallic conductivity of ZrTe3. The calculation of the Fermi surface revealed three branches. The one caused by the intersection ofEFwith bands of predominantly Te chain character shows an extended region of approximately parallel Fermi surface. The nesting vector, which lies in the range q→≈(0.95±0.05)a→*+(0.35±0.15)c→*, is in fair agreement with data from an electron diffraction study of ZrTe3, which has shown the presence of a charge density wave at a temperature of 63 K with the vector q→≈0.93a→*+0.33c→*.