We present observations of HC3N, HC5N, and HC7N in five molecular clouds. Statistical equilibrium calculations have been performed for HC5N and HC7N and compared with our data and data on other transitions of these molecules reported in the literature to derive the densities and the column densities of the cyanopolyynes in these clouds. We derive densities for TMC 1, TMC 2, and Ll544 of between 1 and 4 × 104 cm-3. We have found that the ratios of the cyanopolyynes in these three clouds are the following: HC3N/HC5N ≍ 1.4 and HC5N/HC7N ≍ 3. In Ll34 N and DR 21(OH) we have measured limits on the HC5N emission and find the HC3N/HC5N ratio to be substantially greater than in the three Taurus clouds. We have also compared the cyanopolyyne column densities with those of 13CO and find that the abundance of HC3N in L 134 N and DR 21 (OH)- is an order of magnitude smaller than that found in the Taurus clouds. Tile chemical differences between L l34 N and the Taurus clouds are particularly interesting in view of their similar physical properties.