M109 has three satellite galaxies (UGC 6923, UGC 6940 and UGC 6969) and possibly more. Detailed hydrogen line observations have been obtained from M109 and its satellites. M109's H I (H one) distribution is regular with a low-level radial extension outside the stellar disc, while in the bar is a central H I hole in the gas distribution. Possibly the gas has been transported inwards by the bar, and because of the emptiness of the hole no large accretion events can have happened in the recent past.