We present the initial results of a 3-mm spectral line survey towards 83 methanol maser selected massive star-forming regions .
Here we report observations of the J = 5 – 4 and 6 – 5 rotational transitions of methyl cyanide ( CH _ { 3 } CN ) and the J = 1 – 0 transition of HCO ^ { + } and H ^ { 13 } CO ^ { + } .

CH _ { 3 } CN emission is detected in 58 sources ( 70 % of our sample ) .
We estimate the temperature and column density for 37 of these using the rotational diagram method .
The temperatures we derive range from 28 – 166 K , and are lower than previously reported temperatures , derived from higher J transitions .
We find that CH _ { 3 } CN is brighter and more commonly detected towards ultra-compact H II ( UCH II ) regions than towards isolated maser sources .
Detection of CH _ { 3 } CN towards isolated maser sources strongly suggests that these objects are internally heated and that CH _ { 3 } CN is excited prior to the UCH II phase of massive star-formation .

HCO ^ { + } is detected towards 82 sources ( 99 % of our sample ) , many of which exhibit asymmetric line profiles compared to H ^ { 13 } CO ^ { + } .
Skewed profiles are indicative of inward or outward motions , however , we find approximately equal numbers of red and blue-skewed profiles among all classes .
Column densities are derived from an analysis of the HCO ^ { + } and H ^ { 13 } CO ^ { + } line profiles .

80 sources have mid-infrared counterparts : 68 seen in emission and 12 seen in absorption as ‘ dark clouds ’ .
Seven of the twelve dark clouds exhibit asymmetric HCO ^ { + } profiles , six of which are skewed to the blue , indicating infalling motions .
CH _ { 3 } CN is also common in dark clouds , where it has a 90 % detection rate .