Iv'e heard of the 1 series, 3 series, 5 series, 6 series, and 7 series but not a 2 series or 4 series (apart from the Z4).Was there ever a 2 or 4 series...if not, why?Colin M...really?? I've heard of the Z4 coupé but not a Z2...

There are both, 2 & 4 series are coupe versions.Add: e.g. 2002 68-76 2000C/CS 65-69 2000 66-72

There were initially only odd number series, in the 1970s, but with the advent of the big coupe, they created the E24 6 series which is based upon the E12/E28 5 series chassis. BMW is notorious for both defying their own numbering systems and also paying homage to the classic numbering system (for example, the E36 323i was 2.5 liters but named such to set it apart from the 2.8 liter 328i and also pay respects to the European 323i of the late 70s and early 80s. BMW initially introduced the E90 3 series as a sedan only, however they were toying with the idea of bringing the coupe version out as a 4 series as the 6 series is a coupe version of a 5 series, however at least in North America they abandoned this and retained the 3 series moniker for all E90 based cars, coupes, sedans, convertibles.While the Z3 was based on the E36 3 series platform, the Z4 was named such not due to a difference in vehicle layout but to denote its succession of the Z3.

To be honest, they're probably just holding back on these model numbers and will use them eventually. In these days of niche marketing, it's quite possible that we'll one day see a 2-series as a slightly bigger car than the 1-series, but smaller than a 3-series.

They are not "real" number, 2 and 4.